diff -r f98d3c57906f -r 82555d7186d0 mercurial/filemerge.py
--- a/mercurial/filemerge.py	Fri Aug 24 22:21:04 2018 -0700
+++ b/mercurial/filemerge.py	Wed Aug 22 13:57:01 2018 +0900
@@ -140,9 +140,8 @@
     strictcheck = ui.configbool('merge', 'strict-capability-check')
 
     def hascapability(tool, capability, strict=False):
-        if strict and tool in internals:
-            if internals[tool].capabilities.get(capability):
-                return True
+        if tool in internals:
+            return strict and internals[tool].capabilities.get(capability)
         return _toolbool(ui, tool, capability)
 
     def supportscd(tool):