diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index d56b6031164..992853c0466 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -409,6 +409,9 @@ ir_constant::ir_constant(const struct glsl_type *type, exec_list *value_list)
       return;
    }
 
+   for (unsigned i = 0; i < 16; i++) {
+      this->value.u[i] = 0;
+   }
 
    ir_constant *value = (ir_constant *) (value_list->head);