diff --git a/src/c3nav/site/converters.py b/src/c3nav/site/converters.py
index 62f9e401..38a4a0be 100644
--- a/src/c3nav/site/converters.py
+++ b/src/c3nav/site/converters.py
@@ -12,7 +12,7 @@ class LocationConverter:
 
 
 class CoordinatesConverter:
-    regex = r'[a-z0-9-_.]+:-?\d+(\.\d+)?:-?\d+(\.\d+)?'
+    regex = r'c:[a-z0-9-_.]+:-?\d+(\.\d+)?:-?\d+(\.\d+)?'
 
     def to_python(self, value):
         return value