Index: lib/Index/USRGeneration.cpp
===================================================================
--- lib/Index/USRGeneration.cpp
+++ lib/Index/USRGeneration.cpp
@@ -754,8 +754,12 @@
     if (const FunctionProtoType *FT = T->getAs<FunctionProtoType>()) {
       Out << 'F';
       VisitType(FT->getReturnType());
-      for (const auto &I : FT->param_types())
+      Out << '(';
+      for (const auto &I : FT->param_types()) {
+        Out << '#';
         VisitType(I);
+      }
+      Out << ')';
       if (FT->isVariadic())
         Out << '.';
       return;
Index: test/Index/USR/func-type.cpp
===================================================================
--- /dev/null
+++ test/Index/USR/func-type.cpp
@@ -0,0 +1,13 @@
+// RUN: c-index-test core -print-source-symbols -- %s | FileCheck %s
+
+// Functions taking function pointer parameters with different signatures should result in unique USRs.
+
+typedef void (*_VoidToVoidPtr_)();
+typedef void (*_IntToVoidPtr_)( int );
+typedef _VoidToVoidPtr_ (*IntTo_VoidToVoidPtr_Ptr)( int );
+typedef _IntToVoidPtr_ (*VoidTo_IntToVoidPtr_Ptr)();
+
+void Func( IntTo_VoidToVoidPtr_Ptr );
+// CHECK: {{[0-9]+}}:6 | function/C | Func | c:@F@Func#*F*Fv()(#I)# |
+void Func( VoidTo_IntToVoidPtr_Ptr );
+// CHECK: {{[0-9]+}}:6 | function/C | Func | c:@F@Func#*F*Fv(#I)()# |