diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1125,6 +1125,11 @@
   bool LHSFloat = LHSType->isRealFloatingType();
   bool RHSFloat = RHSType->isRealFloatingType();
 
+  // FIXME: Implement floating to fixed point conversion.(Bug 46268)
+  // Reference N1169 4.1.4 (Type conversion, usual arithmetic conversions).
+  if ((LHSType->isFixedPointType() && RHSFloat) ||
+      (LHSFloat && RHSType->isFixedPointType()))
+    return QualType();
   // If we have two real floating types, convert the smaller operand
   // to the bigger result.
   if (LHSFloat && RHSFloat) {
diff --git a/clang/test/Frontend/fixed_point_errors.c b/clang/test/Frontend/fixed_point_errors.c
--- a/clang/test/Frontend/fixed_point_errors.c
+++ b/clang/test/Frontend/fixed_point_errors.c
@@ -286,3 +286,8 @@
 
 // Division by zero
 short _Accum div_zero = 4.5k / 0.0lr;  // expected-error {{initializer element is not a compile-time constant}}
+
+void foo(void) {
+  _Accum x = 0.5k;
+  if (x == 0.5) {} // expected-error{{invalid operands to binary expression ('_Accum' and 'double')}}
+}