diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index 7462bd8c0..271c6b4d4 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -1148,7 +1148,15 @@ def get_dep_identifier(name, kwargs):
         modlist = [modlist]
     for module in modlist:
         elements.append(module)
-    return '/'.join(elements) + '/main' + str(kwargs.get('main', False)) + '/static' + str(kwargs.get('static', False))
+    # We use a tuple because we need a non-mutable structure to use as the key
+    # of a dictionary and a string has potential for name collisions
+    identifier = tuple(elements)
+    identifier += ('main', kwargs.get('main', False))
+    identifier += ('static', kwargs.get('static', False))
+    if 'fallback' in kwargs:
+        f = kwargs.get('fallback')
+        identifier += ('fallback', f[0], f[1])
+    return identifier
 
 def find_external_dependency(name, environment, kwargs):
     required = kwargs.get('required', True)
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 5a99e1c76..1491767b9 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -1626,7 +1626,9 @@ class Interpreter():
                 dep = dependencies.find_external_dependency(name, self.environment, kwargs)
             except dependencies.DependencyException:
                 if 'fallback' in kwargs:
-                    return self.dependency_fallback(kwargs)
+                    dep = self.dependency_fallback(kwargs)
+                    self.coredata.deps[identifier] = dep.held_object
+                    return dep
                 raise
         self.coredata.deps[identifier] = dep
         return DependencyHolder(dep)