diff --git a/gcc/ada/gnat1drv.adb b/gcc/ada/gnat1drv.adb
index 3afe801efaa6421cc4658b26cd7b921b5bf0b370..40f9228dd5c491cdda1e645196d11d687f40dc8f 100644
--- a/gcc/ada/gnat1drv.adb
+++ b/gcc/ada/gnat1drv.adb
@@ -565,6 +565,10 @@ procedure Gnat1drv is
 
          Tagged_Type_Expansion := False;
 
+         --  Force the use of "error:" prefix for error messages
+
+         Unique_Error_Tag := True;
+
          --  Detect that the runtime library support for floating-point numbers
          --  may not be compatible with SPARK analysis of IEEE-754 floats.