diff --git a/libsolidity/formal/SMTChecker.cpp b/libsolidity/formal/SMTChecker.cpp
index 1da5b291e..8f4abdc27 100644
--- a/libsolidity/formal/SMTChecker.cpp
+++ b/libsolidity/formal/SMTChecker.cpp
@@ -205,7 +205,7 @@ void SMTChecker::endVisit(Assignment const& _assignment)
 			_assignment.location(),
 			"Assertion checker does not yet implement compound assignment."
 		);
-	else if (_assignment.annotation().type->category() != Type::Category::Integer)
+	else if (!SSAVariable::isSupportedType(_assignment.annotation().type->category()))
 		m_errorReporter.warning(
 			_assignment.location(),
 			"Assertion checker does not yet implement type " + _assignment.annotation().type->toString()
@@ -266,14 +266,15 @@ void SMTChecker::endVisit(UnaryOperation const& _op)
 	{
 	case Token::Not: // !
 	{
-		solAssert(_op.annotation().type->category() == Type::Category::Bool, "");
+		solAssert(SSAVariable::isBool(_op.annotation().type->category()), "");
 		defineExpr(_op, !expr(_op.subExpression()));
 		break;
 	}
 	case Token::Inc: // ++ (pre- or postfix)
 	case Token::Dec: // -- (pre- or postfix)
 	{
-		solAssert(_op.annotation().type->category() == Type::Category::Integer, "");
+
+		solAssert(SSAVariable::isInteger(_op.annotation().type->category()), "");
 		solAssert(_op.subExpression().annotation().lValueRequested, "");
 		if (Identifier const* identifier = dynamic_cast<Identifier const*>(&_op.subExpression()))
 		{
@@ -370,7 +371,7 @@ void SMTChecker::endVisit(Identifier const& _identifier)
 	{
 		// Will be translated as part of the node that requested the lvalue.
 	}
-	else if (SSAVariable::supportedType(_identifier.annotation().type.get()))
+	else if (SSAVariable::isSupportedType(_identifier.annotation().type->category()))
 		defineExpr(_identifier, currentValue(*decl));
 	else if (FunctionType const* fun = dynamic_cast<FunctionType const*>(_identifier.annotation().type.get()))
 	{
@@ -444,21 +445,37 @@ void SMTChecker::arithmeticOperation(BinaryOperation const& _op)
 void SMTChecker::compareOperation(BinaryOperation const& _op)
 {
 	solAssert(_op.annotation().commonType, "");
-	if (_op.annotation().commonType->category() == Type::Category::Integer)
+	if (SSAVariable::isSupportedType(_op.annotation().commonType->category()))
 	{
 		smt::Expression left(expr(_op.leftExpression()));
 		smt::Expression right(expr(_op.rightExpression()));
 		Token::Value op = _op.getOperator();
-		smt::Expression value = (
-			op == Token::Equal ? (left == right) :
-			op == Token::NotEqual ? (left != right) :
-			op == Token::LessThan ? (left < right) :
-			op == Token::LessThanOrEqual ? (left <= right) :
-			op == Token::GreaterThan ? (left > right) :
-			/*op == Token::GreaterThanOrEqual*/ (left >= right)
-		);
+		shared_ptr<smt::Expression> value;
+		if (SSAVariable::isInteger(_op.annotation().commonType->category()))
+		{
+			value = make_shared<smt::Expression>(
+				op == Token::Equal ? (left == right) :
+				op == Token::NotEqual ? (left != right) :
+				op == Token::LessThan ? (left < right) :
+				op == Token::LessThanOrEqual ? (left <= right) :
+				op == Token::GreaterThan ? (left > right) :
+				/*op == Token::GreaterThanOrEqual*/ (left >= right)
+			);
+		}
+		else // Bool
+		{
+			solAssert(SSAVariable::isBool(_op.annotation().commonType->category()), "");
+			value = make_shared<smt::Expression>(
+				op == Token::Equal ? (left == right) :
+				op == Token::NotEqual ? (left != right) :
+				op == Token::LessThan ? (!left && right) :
+				op == Token::LessThanOrEqual ? (!left || right) :
+				op == Token::GreaterThan ? (left && !right) :
+				/*op == Token::GreaterThanOrEqual*/ (left || !right)
+			);
+		}
 		// TODO: check that other values for op are not possible.
-		defineExpr(_op, value);
+		defineExpr(_op, *value);
 	}
 	else
 		m_errorReporter.warning(
@@ -728,10 +745,10 @@ void SMTChecker::mergeVariables(vector<Declaration const*> const& _variables, sm
 
 bool SMTChecker::createVariable(VariableDeclaration const& _varDecl)
 {
-	if (SSAVariable::supportedType(_varDecl.type().get()))
+	if (SSAVariable::isSupportedType(_varDecl.type()->category()))
 	{
 		solAssert(m_variables.count(&_varDecl) == 0, "");
-		m_variables.emplace(&_varDecl, SSAVariable(&_varDecl, *m_interface));
+		m_variables.emplace(&_varDecl, SSAVariable(_varDecl, *m_interface));
 		return true;
 	}
 	else
diff --git a/libsolidity/formal/SSAVariable.cpp b/libsolidity/formal/SSAVariable.cpp
index 4e6bcbcb5..f3213e03c 100644
--- a/libsolidity/formal/SSAVariable.cpp
+++ b/libsolidity/formal/SSAVariable.cpp
@@ -17,6 +17,7 @@
 
 #include <libsolidity/formal/SSAVariable.h>
 
+#include <libsolidity/formal/SymbolicBoolVariable.h>
 #include <libsolidity/formal/SymbolicIntVariable.h>
 
 #include <libsolidity/ast/AST.h>
@@ -26,23 +27,35 @@ using namespace dev;
 using namespace dev::solidity;
 
 SSAVariable::SSAVariable(
-	Declaration const* _decl,
+	Declaration const& _decl,
 	smt::SolverInterface& _interface
 )
 {
 	resetIndex();
 
-	if (dynamic_cast<IntegerType const*>(_decl->type().get()))
+	if (isInteger(_decl.type()->category()))
 		m_symbolicVar = make_shared<SymbolicIntVariable>(_decl, _interface);
+	else if (isBool(_decl.type()->category()))
+		m_symbolicVar = make_shared<SymbolicBoolVariable>(_decl, _interface);
 	else
 	{
 		solAssert(false, "");
 	}
 }
 
-bool SSAVariable::supportedType(Type const* _decl)
+bool SSAVariable::isSupportedType(Type::Category _category)
 {
-	return dynamic_cast<IntegerType const*>(_decl);
+	return isInteger(_category) || isBool(_category);
+}
+
+bool SSAVariable::isInteger(Type::Category _category)
+{
+	return _category == Type::Category::Integer;
+}
+
+bool SSAVariable::isBool(Type::Category _category)
+{
+	return _category == Type::Category::Bool;
 }
 
 void SSAVariable::resetIndex()
diff --git a/libsolidity/formal/SSAVariable.h b/libsolidity/formal/SSAVariable.h
index 275e85900..bf5dae3b5 100644
--- a/libsolidity/formal/SSAVariable.h
+++ b/libsolidity/formal/SSAVariable.h
@@ -37,7 +37,7 @@ public:
 	/// @param _decl Used to determine the type and forwarded to the symbolic var.
 	/// @param _interface Forwarded to the symbolic var such that it can give constraints to the solver.
 	SSAVariable(
-		Declaration const* _decl,
+		Declaration const& _decl,
 		smt::SolverInterface& _interface
 	);
 
@@ -68,8 +68,10 @@ public:
 	void setZeroValue();
 	void setUnknownValue();
 
-	/// So far Int is supported.
-	static bool supportedType(Type const* _decl);
+	/// So far Int and Bool are supported.
+	static bool isSupportedType(Type::Category _category);
+	static bool isInteger(Type::Category _category);
+	static bool isBool(Type::Category _category);
 
 private:
 	smt::Expression valueAtSequence(int _seq) const
diff --git a/libsolidity/formal/SolverInterface.h b/libsolidity/formal/SolverInterface.h
index 884873100..0bdebb6c7 100644
--- a/libsolidity/formal/SolverInterface.h
+++ b/libsolidity/formal/SolverInterface.h
@@ -46,7 +46,8 @@ enum class Sort
 {
 	Int,
 	Bool,
-	IntIntFun // Function of one Int returning a single Int
+	IntIntFun, // Function of one Int returning a single Int
+	IntBoolFun // Function of one Int returning a single Bool
 };
 
 /// C++ representation of an SMTLIB2 expression.
@@ -132,10 +133,22 @@ public:
 	Expression operator()(Expression _a) const
 	{
 		solAssert(
-			sort == Sort::IntIntFun && arguments.empty(),
+			arguments.empty(),
 			"Attempted function application to non-function."
 		);
-		return Expression(name, _a, Sort::Int);
+		switch (sort)
+		{
+		case Sort::IntIntFun:
+			return Expression(name, _a, Sort::Int);
+		case Sort::IntBoolFun:
+			return Expression(name, _a, Sort::Bool);
+		default:
+			solAssert(
+				false,
+				"Attempted function application to invalid type."
+			);
+			break;
+		}
 	}
 
 	std::string const name;
@@ -167,9 +180,18 @@ public:
 
 	virtual Expression newFunction(std::string _name, Sort _domain, Sort _codomain)
 	{
-		solAssert(_domain == Sort::Int && _codomain == Sort::Int, "Function sort not supported.");
+		solAssert(_domain == Sort::Int, "Function sort not supported.");
 		// Subclasses should do something here
-		return Expression(std::move(_name), {}, Sort::IntIntFun);
+		switch (_codomain)
+		{
+		case Sort::Int:
+			return Expression(std::move(_name), {}, Sort::IntIntFun);
+		case Sort::Bool:
+			return Expression(std::move(_name), {}, Sort::IntBoolFun);
+		default:
+			solAssert(false, "Function sort not supported.");
+			break;
+		}
 	}
 	virtual Expression newInteger(std::string _name)
 	{
diff --git a/libsolidity/formal/SymbolicBoolVariable.cpp b/libsolidity/formal/SymbolicBoolVariable.cpp
new file mode 100644
index 000000000..e5c56e461
--- /dev/null
+++ b/libsolidity/formal/SymbolicBoolVariable.cpp
@@ -0,0 +1,43 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <libsolidity/formal/SymbolicBoolVariable.h>
+
+#include <libsolidity/ast/AST.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
+SymbolicBoolVariable::SymbolicBoolVariable(
+	Declaration const& _decl,
+	smt::SolverInterface&_interface
+):
+	SymbolicVariable(_decl, _interface)
+{
+	solAssert(m_declaration.type()->category() == Type::Category::Bool, "");
+	m_expression = make_shared<smt::Expression>(m_interface.newFunction(uniqueSymbol(), smt::Sort::Int, smt::Sort::Bool));
+}
+
+void SymbolicBoolVariable::setZeroValue(int _seq)
+{
+	m_interface.addAssertion(valueAtSequence(_seq) == smt::Expression(false));
+}
+
+void SymbolicBoolVariable::setUnknownValue(int)
+{
+}
diff --git a/libsolidity/formal/SymbolicBoolVariable.h b/libsolidity/formal/SymbolicBoolVariable.h
new file mode 100644
index 000000000..3510b7703
--- /dev/null
+++ b/libsolidity/formal/SymbolicBoolVariable.h
@@ -0,0 +1,47 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <libsolidity/formal/SymbolicVariable.h>
+
+#include <libsolidity/ast/Types.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+/**
+ * Specialization of SymbolicVariable for Bool
+ */
+class SymbolicBoolVariable: public SymbolicVariable
+{
+public:
+	SymbolicBoolVariable(
+		Declaration const& _decl,
+		smt::SolverInterface& _interface
+	);
+
+	/// Sets the var to false.
+	void setZeroValue(int _seq);
+	/// Does nothing since the SMT solver already knows the valid values.
+	void setUnknownValue(int _seq);
+};
+
+}
+}
diff --git a/libsolidity/formal/SymbolicIntVariable.cpp b/libsolidity/formal/SymbolicIntVariable.cpp
index d08dc1553..eb7b1c175 100644
--- a/libsolidity/formal/SymbolicIntVariable.cpp
+++ b/libsolidity/formal/SymbolicIntVariable.cpp
@@ -24,12 +24,12 @@ using namespace dev;
 using namespace dev::solidity;
 
 SymbolicIntVariable::SymbolicIntVariable(
-	Declaration const* _decl,
+	Declaration const& _decl,
 	smt::SolverInterface& _interface
 ):
 	SymbolicVariable(_decl, _interface)
 {
-	solAssert(m_declaration->type()->category() == Type::Category::Integer, "");
+	solAssert(m_declaration.type()->category() == Type::Category::Integer, "");
 	m_expression = make_shared<smt::Expression>(m_interface.newFunction(uniqueSymbol(), smt::Sort::Int, smt::Sort::Int));
 }
 
@@ -40,7 +40,7 @@ void SymbolicIntVariable::setZeroValue(int _seq)
 
 void SymbolicIntVariable::setUnknownValue(int _seq)
 {
-	auto const& intType = dynamic_cast<IntegerType const&>(*m_declaration->type());
+	auto const& intType = dynamic_cast<IntegerType const&>(*m_declaration.type());
 	m_interface.addAssertion(valueAtSequence(_seq) >= minValue(intType));
 	m_interface.addAssertion(valueAtSequence(_seq) <= maxValue(intType));
 }
diff --git a/libsolidity/formal/SymbolicIntVariable.h b/libsolidity/formal/SymbolicIntVariable.h
index afa25f1b9..eb36b8996 100644
--- a/libsolidity/formal/SymbolicIntVariable.h
+++ b/libsolidity/formal/SymbolicIntVariable.h
@@ -33,7 +33,7 @@ class SymbolicIntVariable: public SymbolicVariable
 {
 public:
 	SymbolicIntVariable(
-		Declaration const* _decl,
+		Declaration const& _decl,
 		smt::SolverInterface& _interface
 	);
 
diff --git a/libsolidity/formal/SymbolicVariable.cpp b/libsolidity/formal/SymbolicVariable.cpp
index 629049ea5..d59b55b10 100644
--- a/libsolidity/formal/SymbolicVariable.cpp
+++ b/libsolidity/formal/SymbolicVariable.cpp
@@ -24,7 +24,7 @@ using namespace dev;
 using namespace dev::solidity;
 
 SymbolicVariable::SymbolicVariable(
-	Declaration const* _decl,
+	Declaration const& _decl,
 	smt::SolverInterface& _interface
 ):
 	m_declaration(_decl),
@@ -34,7 +34,7 @@ SymbolicVariable::SymbolicVariable(
 
 string SymbolicVariable::uniqueSymbol() const
 {
-	return m_declaration->name() + "_" + to_string(m_declaration->id());
+	return m_declaration.name() + "_" + to_string(m_declaration.id());
 }
 
 
diff --git a/libsolidity/formal/SymbolicVariable.h b/libsolidity/formal/SymbolicVariable.h
index 932582503..75eb9fa5c 100644
--- a/libsolidity/formal/SymbolicVariable.h
+++ b/libsolidity/formal/SymbolicVariable.h
@@ -37,7 +37,7 @@ class SymbolicVariable
 {
 public:
 	SymbolicVariable(
-		Declaration const* _decl,
+		Declaration const& _decl,
 		smt::SolverInterface& _interface
 	);
 
@@ -60,7 +60,7 @@ protected:
 		return (*m_expression)(_seq);
 	}
 
-	Declaration const* m_declaration;
+	Declaration const& m_declaration;
 	std::shared_ptr<smt::Expression> m_expression = nullptr;
 	smt::SolverInterface& m_interface;
 };
diff --git a/test/libsolidity/SMTChecker.cpp b/test/libsolidity/SMTChecker.cpp
index 12b5f4396..beb933a4e 100644
--- a/test/libsolidity/SMTChecker.cpp
+++ b/test/libsolidity/SMTChecker.cpp
@@ -329,6 +329,144 @@ BOOST_AUTO_TEST_CASE(ways_to_merge_variables)
 	CHECK_WARNING(text, "Assertion violation happens here");
 }
 
+BOOST_AUTO_TEST_CASE(bool_simple)
+{
+	string text = R"(
+		contract C {
+			function f(bool x) public pure {
+				assert(x);
+			}
+		}
+	)";
+	CHECK_WARNING(text, "Assertion violation happens here");
+	text = R"(
+		contract C {
+			function f(bool x, bool y) public pure {
+				assert(x == y);
+			}
+		}
+	)";
+	CHECK_WARNING(text, "Assertion violation happens here");
+	text = R"(
+		contract C {
+			function f(bool x, bool y) public pure {
+				bool z = x || y;
+				assert(!(x && y) || z);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				if(x) {
+					assert(x);
+				} else {
+					assert(!x);
+				}
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				bool y = x;
+				assert(x == y);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				require(x);
+				bool y;
+				y = false;
+				assert(x || y);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				bool y;
+				assert(x <= y);
+			}
+		}
+	)";
+	CHECK_WARNING(text, "Assertion violation happens here");
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				bool y;
+				assert(x >= y);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x) public pure {
+				require(x);
+				bool y;
+				assert(x > y);
+				assert(y < x);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+}
+
+BOOST_AUTO_TEST_CASE(bool_int_mixed)
+{
+	string text = R"(
+		contract C {
+			function f(bool x) public pure {
+				uint a;
+				if(x)
+					a = 1;
+				assert(!x || a > 0);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x, uint a) public pure {
+				require(!x || a > 0);
+				uint b = a;
+				assert(!x || b > 0);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+	text = R"(
+		contract C {
+			function f(bool x, bool y) public pure {
+				uint a;
+				if (x) {
+					if (y) {
+						a = 0;
+					} else {
+						a = 1;
+					}
+				} else {
+					if (y) {
+						a = 1;
+					} else {
+						a = 0;
+					}
+				}
+				bool xor_x_y = (x && !y) || (!x && y);
+				assert(!xor_x_y || a > 0);
+			}
+		}
+	)";
+	CHECK_SUCCESS_NO_WARNINGS(text);
+}
+
 BOOST_AUTO_TEST_CASE(while_loop_simple)
 {
 	// Check that variables are cleared