diff --git a/Changelog.md b/Changelog.md
index 5a421fa5a..1e16df590 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -110,6 +110,7 @@ Bugfixes:
  * Type Checker: Fix freeze for negative fixed-point literals very close to ``0``, such as ``-1e-100``.
  * Type Checker: Report error when using structs in events without experimental ABIEncoderV2. This used to crash or log the wrong values.
  * Type Checker: Report error when using indexed structs in events with experimental ABIEncoderV2. This used to log wrong values.
+ * Type Checker: Dynamic types as key for public mappings return error instead of assertion fail.
  * Type System: Allow arbitrary exponents for literals with a mantissa of zero.
 
 ### 0.4.24 (2018-05-16)
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 5033fd63f..fca64f6a8 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -819,7 +819,9 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 	)
 		m_errorReporter.typeError(_variable.location(), "Internal or recursive type is not allowed for public state variables.");
 
-	if (varType->category() == Type::Category::Array)
+	switch (varType->category())
+	{
+	case Type::Category::Array:
 		if (auto arrayType = dynamic_cast<ArrayType const*>(varType.get()))
 			if (
 				((arrayType->location() == DataLocation::Memory) ||
@@ -827,6 +829,18 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 				!arrayType->validForCalldata()
 			)
 				m_errorReporter.typeError(_variable.location(), "Array is too large to be encoded.");
+		break;
+	case Type::Category::Mapping:
+		if (auto mappingType = dynamic_cast<MappingType const*>(varType.get()))
+			if (
+				mappingType->keyType()->isDynamicallySized() &&
+				_variable.visibility() == Declaration::Visibility::Public
+			)
+				m_errorReporter.typeError(_variable.location(), "Dynamically-sized keys for public mappings are not supported.");
+		break;
+	default:
+		break;
+	}
 
 	return false;
 }
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_1.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_1.sol
new file mode 100644
index 000000000..ea2d282cc
--- /dev/null
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_1.sol
@@ -0,0 +1,5 @@
+contract c {
+	mapping(uint[] => uint) data;
+}
+// ----
+// ParserError: (26-27): Expected '=>' but got '['
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol
new file mode 100644
index 000000000..713cddeb3
--- /dev/null
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_2.sol
@@ -0,0 +1,8 @@
+contract c {
+	struct S {
+		uint x;
+	}
+	mapping(S => uint) data;
+}
+// ----
+// ParserError: (47-48): Expected elementary type name for mapping key type
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol
new file mode 100644
index 000000000..655af9de7
--- /dev/null
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_3.sol
@@ -0,0 +1,8 @@
+contract c {
+	struct S {
+		string s;
+	}
+	mapping(S => uint) data;
+}
+// ----
+// ParserError: (49-50): Expected elementary type name for mapping key type
diff --git a/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_4.sol b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_4.sol
new file mode 100644
index 000000000..f4dcb00ad
--- /dev/null
+++ b/test/libsolidity/syntaxTests/parsing/mapping_nonelementary_key_4.sol
@@ -0,0 +1,5 @@
+contract c {
+	mapping(string[] => uint) data;
+}
+// ----
+// ParserError: (28-29): Expected '=>' but got '['
diff --git a/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key.sol b/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key.sol
new file mode 100644
index 000000000..825ee09a9
--- /dev/null
+++ b/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key.sol
@@ -0,0 +1,3 @@
+contract c {
+	mapping(string => uint) data;
+}
diff --git a/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key_public.sol b/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key_public.sol
new file mode 100644
index 000000000..9fb575afd
--- /dev/null
+++ b/test/libsolidity/syntaxTests/types/mapping/mapping_dynamic_key_public.sol
@@ -0,0 +1,5 @@
+contract c {
+	mapping(string => uint) public data;
+}
+// ----
+// TypeError: (14-49): Dynamically-sized keys for public mappings are not supported.