diff --git a/libsolidity/codegen/CompilerContext.cpp b/libsolidity/codegen/CompilerContext.cpp
index 398e362f5..6de51298d 100644
--- a/libsolidity/codegen/CompilerContext.cpp
+++ b/libsolidity/codegen/CompilerContext.cpp
@@ -286,7 +286,11 @@ FunctionDefinition const& CompilerContext::superFunction(FunctionDefinition cons
 	solAssert(m_mostDerivedContract, "No most derived contract set.");
 	ContractDefinition const* super = _base.superContract(mostDerivedContract());
 	solAssert(super, "Super contract not available.");
-	return _function.resolveVirtual(mostDerivedContract(), super);
+
+	FunctionDefinition const& resolvedFunction = _function.resolveVirtual(mostDerivedContract(), super);
+	solAssert(resolvedFunction.isImplemented(), "");
+
+	return resolvedFunction;
 }
 
 ContractDefinition const& CompilerContext::mostDerivedContract() const
diff --git a/libsolidity/codegen/ContractCompiler.cpp b/libsolidity/codegen/ContractCompiler.cpp
index 5afa4d26f..fca076b65 100644
--- a/libsolidity/codegen/ContractCompiler.cpp
+++ b/libsolidity/codegen/ContractCompiler.cpp
@@ -604,6 +604,8 @@ bool ContractCompiler::visit(VariableDeclaration const& _variableDeclaration)
 
 bool ContractCompiler::visit(FunctionDefinition const& _function)
 {
+	solAssert(_function.isImplemented(), "");
+
 	CompilerContext::LocationSetter locationSetter(m_context, _function);
 
 	m_context.startFunction(_function);
diff --git a/test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_fail.sol b/test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_and_implemented_with_unimplemented.sol
similarity index 100%
rename from test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_fail.sol
rename to test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_and_implemented_with_unimplemented.sol
diff --git a/test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_fine.sol b/test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_and_unimplemented_with_unimplemented.sol
similarity index 100%
rename from test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_fine.sol
rename to test/libsolidity/syntaxTests/inheritance/override/override_unimplemented_and_unimplemented_with_unimplemented.sol
diff --git a/test/libsolidity/syntaxTests/modifiers/cross_contract_super.sol b/test/libsolidity/syntaxTests/modifiers/cross_contract_super.sol
new file mode 100644
index 000000000..b70ba3092
--- /dev/null
+++ b/test/libsolidity/syntaxTests/modifiers/cross_contract_super.sol
@@ -0,0 +1,9 @@
+contract C {
+    modifier m() { _; }
+}
+contract D is C {
+    function f() super.m public {
+    }
+}
+// ----
+// DeclarationError 7920: (74-81): Identifier not found or not unique.