diff --git a/master/buildbot/flathub_master.py b/master/buildbot/flathub_master.py
index 8a42961a41..990c4d5d98 100644
--- a/master/buildbot/flathub_master.py
+++ b/master/buildbot/flathub_master.py
@@ -1342,17 +1342,35 @@ def run(self):
             # This strips /* comments */
             manifest = json.loads(re.sub(r'/\*.*?\*/', '', manifest_content))
 
+        sdk_name = manifest["sdk"]
+
+        # Check if SDK version is specified in ref form
+        if "//" in sdk_name:
+            sdk_version = manifest["sdk"].split("//")[-1]
+        else:
+            sdk_version = manifest["runtime-version"]
+
         # Get all runtimes to check for available architectures later
         runtimes = get_runtimes('flathub')
-        if not runtimes.get(manifest["sdk"], {}).get(manifest["runtime-version"], []) and flathub_branch in ('test', 'beta'):
+        if not runtimes.get(sdk_name, {}).get(sdk_version, []) and flathub_default_branch in ('test', 'beta'):
             # Check also in flathub-beta for test and beta builds
             runtimes = get_runtimes('flathub-beta')
 
         sdk_arches = set(runtimes.get(manifest["sdk"], {}).get(manifest["runtime-version"], []))
+        if len(sdk_arches) == 0:
+            self.descriptionDone = ["Could not find requested SDK"]
+            defer.returnValue(FAILURE)
+            return
+
         if "sdk-extensions" in manifest:
             for extension in manifest["sdk-extensions"]:
-                if runtimes.get(extension, {}).get(manifest["runtime-version"], []):
-                    sdk_arches = sdk_arches & set(runtimes[extension][manifest["runtime-version"]])
+                if runtimes.get(extension, {}).get(sdk_version, []):
+                    sdk_arches = sdk_arches & set(runtimes[extension][sdk_version])
+
+            if len(sdk_arches) == 0:
+                self.descriptionDone = ["Could not find requested SDK extensions"]
+                defer.returnValue(FAILURE)
+                return
 
         # This could have been set by the change event, otherwise look in config or default
         flathub_arches_prop = props.getProperty('flathub_arches', None)
@@ -1375,7 +1393,7 @@ def run(self):
                 return
 
         if len(flathub_arches_prop) == 0:
-            self.descriptionDone = ["No build arch specified or no compatible SDK has been found"]
+            self.descriptionDone = ["No compatible architectures found for required SDK or SDK extensions"]
             defer.returnValue(FAILURE)
             return