diff --git a/liblangutil/Scanner.cpp b/liblangutil/Scanner.cpp
index 3463783bf1dc..9b609ceb0565 100644
--- a/liblangutil/Scanner.cpp
+++ b/liblangutil/Scanner.cpp
@@ -596,7 +596,12 @@ void Scanner::scanToken()
 				token = Token::Period;
 			break;
 		case ':':
-			token = selectToken(Token::Colon);
+			// : :=
+			advance();
+			if (m_char == '=')
+				token = selectToken(Token::AssemblyAssign);
+			else
+				token = Token::Colon;
 			break;
 		case ';':
 			token = selectToken(Token::Semicolon);
diff --git a/liblangutil/Token.h b/liblangutil/Token.h
index 6830e6c24747..0e0801decba4 100644
--- a/liblangutil/Token.h
+++ b/liblangutil/Token.h
@@ -88,6 +88,7 @@ namespace langutil
 	/* Assignment operators. */										\
 	/* IsAssignmentOp() relies on this block of enum values being */	\
 	/* contiguous and sorted in the same order!*/						\
+	T(AssemblyAssign, ":=", 2)                                                   \
 	T(Assign, "=", 2)                                                   \
 	/* The following have to be in exactly the same order as the simple binary operators*/ \
 	T(AssignBitOr, "|=", 2)                                           \
diff --git a/libyul/AsmParser.cpp b/libyul/AsmParser.cpp
index 217c838a712b..3c52cfe95702 100644
--- a/libyul/AsmParser.cpp
+++ b/libyul/AsmParser.cpp
@@ -158,22 +158,21 @@ Statement Parser::parseStatement()
 		}
 		while (currentToken() == Token::Comma);
 
-		expectToken(Token::Colon);
-		expectToken(Token::Assign);
+		expectToken(Token::AssemblyAssign);
 
 		assignment.value.reset(new Expression(parseExpression()));
 		assignment.location.end = locationOf(*assignment.value).end;
 		return Statement{std::move(assignment)};
 	}
+	case Token::AssemblyAssign:
 	case Token::Colon:
 	{
 		if (elementary.type() != typeid(Identifier))
 			fatalParserError("Label name / variable name must precede \":\".");
 		Identifier const& identifier = boost::get<Identifier>(elementary);
-		advance();
 		// identifier:=: should be parsed as identifier: =: (i.e. a label),
 		// while identifier:= (being followed by a non-colon) as identifier := (assignment).
-		if (currentToken() == Token::Assign && peekNextToken() != Token::Colon)
+		if (currentToken() == Token::AssemblyAssign && peekNextToken() != Token::Colon)
 		{
 			Assignment assignment = createWithLocation<Assignment>(identifier.location);
 			if (m_dialect->builtin(identifier.name))
@@ -188,6 +187,9 @@ Statement Parser::parseStatement()
 		}
 		else
 		{
+			if (currentToken() == Token::Colon)
+				advance();
+
 			// label
 			if (m_dialect->flavour != AsmFlavour::Loose)
 				fatalParserError("Labels are not supported.");
@@ -439,10 +441,9 @@ VariableDeclaration Parser::parseVariableDeclaration()
 		else
 			break;
 	}
-	if (currentToken() == Token::Colon)
+	if (currentToken() == Token::AssemblyAssign)
 	{
-		expectToken(Token::Colon);
-		expectToken(Token::Assign);
+		expectToken(Token::AssemblyAssign);
 		varDecl.value = make_unique<Expression>(parseExpression());
 		varDecl.location.end = locationOf(*varDecl.value).end;
 	}
diff --git a/test/libsolidity/syntaxTests/inlineAssembly/invalid/missing_variable_in_assign.sol b/test/libsolidity/syntaxTests/inlineAssembly/invalid/missing_variable_in_assign.sol
index c898433340dc..84d72c2d4091 100644
--- a/test/libsolidity/syntaxTests/inlineAssembly/invalid/missing_variable_in_assign.sol
+++ b/test/libsolidity/syntaxTests/inlineAssembly/invalid/missing_variable_in_assign.sol
@@ -7,5 +7,5 @@ contract C {
   }
 }
 // ----
-// ParserError: (87-88): Literal, identifier or instruction expected.
-// ParserError: (87-88): Expected primary expression.
+// ParserError: (87-89): Literal, identifier or instruction expected.
+// ParserError: (87-89): Expected primary expression.
diff --git a/test/libsolidity/syntaxTests/inlineAssembly/invalid/whitespace_in_assignment.sol b/test/libsolidity/syntaxTests/inlineAssembly/invalid/whitespace_in_assignment.sol
new file mode 100644
index 000000000000..e3444b3894fe
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inlineAssembly/invalid/whitespace_in_assignment.sol
@@ -0,0 +1,10 @@
+contract C {
+  function f() public pure {
+    assembly {
+      let x : = mload(0)
+    }
+  }
+}
+// ----
+// ParserError: (69-70): Literal, identifier or instruction expected.
+// ParserError: (69-70): Expected primary expression.