diff --git a/src/compiler/glsl/ir_function.cpp b/src/compiler/glsl/ir_function.cpp
index 97262f0f4b9..a38e5285292 100644
--- a/src/compiler/glsl/ir_function.cpp
+++ b/src/compiler/glsl/ir_function.cpp
@@ -329,6 +329,9 @@ ir_function::matching_signature(_mesa_glsl_parse_state *state,
          free(inexact_matches);
          return sig;
       case PARAMETER_LIST_INEXACT_MATCH:
+         /* Subroutine signatures must match exactly */
+         if (this->is_subroutine)
+            continue;
          inexact_matches_temp = (ir_function_signature **)
                realloc(inexact_matches,
                        sizeof(*inexact_matches) *