diff --git a/src/libsysprof/sysprof-memprof-source.c b/src/libsysprof/sysprof-memprof-source.c
index aba55e5a..790ba5ef 100644
--- a/src/libsysprof/sysprof-memprof-source.c
+++ b/src/libsysprof/sysprof-memprof-source.c
@@ -49,7 +49,7 @@ sysprof_memprof_source_modify_spawn (SysprofSource    *source,
     else
       sysprof_spawnable_setenv (spawnable,
                                 "LD_PRELOAD",
-                                (freeme = g_strdup_printf ("%s,%s", so_path, ld_preload)));
+                                (freeme = g_strdup_printf ("%s:%s", so_path, ld_preload)));
   }
 #endif
 }
diff --git a/src/libsysprof/sysprof-preload-source.c b/src/libsysprof/sysprof-preload-source.c
index a0af7e1c..fa04f773 100644
--- a/src/libsysprof/sysprof-preload-source.c
+++ b/src/libsysprof/sysprof-preload-source.c
@@ -56,7 +56,7 @@ sysprof_preload_source_modify_spawn (SysprofSource    *source,
       else
         sysprof_spawnable_setenv (spawnable,
                                   "LD_PRELOAD",
-                                  (freeme = g_strdup_printf ("%s,%s", self->preload, ld_preload)));
+                                  (freeme = g_strdup_printf ("%s:%s", self->preload, ld_preload)));
     }
 #endif
 }