diff --git a/master.cfg b/master.cfg
--- a/master.cfg
+++ b/master.cfg
@@ -1293,7 +1293,8 @@ class RunTestGDBSolaris_Common (BuildAnd
         # build/23676.  This can be avoided either by performing a -g
         # -O build or with --disable-unit-tests from Sergio's proposed
         # patch.
-        self.disable_default_compilation_flags = True
+        self.extra_CFLAGS = [ '-O' ]
+        self.extra_CXXFLAGS = self.extra_CFLAGS
         BuildAndTestGDBFactory.__init__ (self, **kwargs)
 
 class RunTestGDBPlainSolaris_c64 (RunTestGDBSolaris_Common):
@@ -1309,7 +1310,8 @@ class RunTestGDBPlainSolaris_c64 (RunTes
         # build/23676.  This can be avoided either by performing a -g
         # -O build or with --disable-unit-tests from Sergio's proposed
         # patch.
-        self.disable_default_compilation_flags = True
+        self.extra_CFLAGS = [ '-O' ]
+        self.extra_CXXFLAGS = self.extra_CFLAGS
         BuildAndTestGDBFactory.__init__ (self, **kwargs)
 
 # Classes needed for ARM (running on Aarch64, on Yao's buildslave)