diff --git a/Compiler.h b/Compiler.h
index 8471fae2a..e83d1ed3a 100644
--- a/Compiler.h
+++ b/Compiler.h
@@ -30,7 +30,7 @@ namespace solidity {
 class Compiler: private ASTConstVisitor
 {
 public:
-	explicit Compiler(bool _optimize = false): m_optimize(_optimize), m_returnTag(m_context.newTag()) {}
+	explicit Compiler(bool _optimize = false): m_optimize(_optimize), m_context(), m_returnTag(m_context.newTag()) {}
 
 	void compileContract(ContractDefinition const& _contract, std::vector<MagicVariableDeclaration const*> const& _magicGlobals,
 						 std::map<ContractDefinition const*, bytes const*> const& _contracts);
diff --git a/CompilerStack.h b/CompilerStack.h
index 358c8fb77..e7143b7bb 100644
--- a/CompilerStack.h
+++ b/CompilerStack.h
@@ -113,7 +113,7 @@ private:
 
 	struct Contract
 	{
-		ContractDefinition const* contract;
+		ContractDefinition const* contract = nullptr;
 		std::shared_ptr<Compiler> compiler;
 		bytes bytecode;
 		std::shared_ptr<InterfaceHandler> interfaceHandler;
diff --git a/ExpressionCompiler.h b/ExpressionCompiler.h
index 67b16aac0..c0ee4ab48 100644
--- a/ExpressionCompiler.h
+++ b/ExpressionCompiler.h
@@ -146,12 +146,12 @@ private:
 
 	private:
 		CompilerContext* m_context;
-		LValueType m_type;
+		LValueType m_type = NONE;
 		/// If m_type is STACK, this is base stack offset (@see
 		/// CompilerContext::getBaseStackOffsetOfVariable) of a local variable.
-		unsigned m_baseStackOffset;
+		unsigned m_baseStackOffset = 0;
 		/// Size of the value of this lvalue on the stack.
-		unsigned m_stackSize;
+		unsigned m_stackSize = 0;
 	};
 
 	bool m_optimize;
diff --git a/GlobalContext.h b/GlobalContext.h
index 50a21f702..c6e35f504 100644
--- a/GlobalContext.h
+++ b/GlobalContext.h
@@ -56,7 +56,7 @@ public:
 
 private:
 	std::vector<std::shared_ptr<MagicVariableDeclaration const>> m_magicVariables;
-	ContractDefinition const* m_currentContract;
+	ContractDefinition const* m_currentContract = nullptr;
 	std::map<ContractDefinition const*, std::shared_ptr<MagicVariableDeclaration const>> mutable m_thisPointer;
 };
 
diff --git a/NameAndTypeResolver.h b/NameAndTypeResolver.h
index 23ac5fe77..1032a87cf 100644
--- a/NameAndTypeResolver.h
+++ b/NameAndTypeResolver.h
@@ -69,7 +69,7 @@ private:
 	/// not contain code.
 	std::map<ASTNode const*, DeclarationContainer> m_scopes;
 
-	DeclarationContainer* m_currentScope;
+	DeclarationContainer* m_currentScope = nullptr;
 };
 
 /**