diff --git a/CHANGES b/CHANGES
index 6b777831a1..b2bd5da1e9 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,8 @@
 
+3.3.0-dev.426 | 2020-10-14 10:47:37 -0700
+
+  * GH-1211: Improve error message for already-defined functions (Jon Siwek, Corelight)
+
 3.3.0-dev.422 | 2020-10-13 16:26:24 -0700
 
   * GH-1208: Use Dictionary validity assertions only during CI (Jon Siwek, Corelight)
diff --git a/VERSION b/VERSION
index a9fa5e6c55..a9c83441c6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.3.0-dev.422
+3.3.0-dev.426
diff --git a/src/Var.cc b/src/Var.cc
index fa1db6c3d1..a0adcb8f4f 100644
--- a/src/Var.cc
+++ b/src/Var.cc
@@ -583,7 +583,7 @@ void begin_func(IDPtr id, const char* module_name,
 
 		case FUNC_FLAVOR_FUNCTION:
 			if ( ! id->IsRedefinable() )
-				id->Error("already defined");
+				id->Error("already defined", t.get());
 			break;
 
 		default:
@@ -594,6 +594,10 @@ void begin_func(IDPtr id, const char* module_name,
 	else
 		id->SetType(t);
 
+	if ( IsErrorType(id->GetType()->Tag()) )
+		reporter->FatalError("invalid definition of '%s' (see previous errors)",
+		                     id->Name());
+
 	const auto& args = t->Params();
 	const auto& canon_args = id->GetType()->AsFuncType()->Params();
 
diff --git a/testing/btest/Baseline/language.function-already-defined/out b/testing/btest/Baseline/language.function-already-defined/out
new file mode 100644
index 0000000000..fcbb88a3e5
--- /dev/null
+++ b/testing/btest/Baseline/language.function-already-defined/out
@@ -0,0 +1,2 @@
+error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.function-already-defined/function-already-defined.zeek, line 4 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.function-already-defined/function-already-defined.zeek, line 7: already defined (foo)
+fatal error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.function-already-defined/function-already-defined.zeek, line 8: invalid definition of 'foo' (see previous errors)
diff --git a/testing/btest/language/function-already-defined.zeek b/testing/btest/language/function-already-defined.zeek
new file mode 100644
index 0000000000..9c609a68ac
--- /dev/null
+++ b/testing/btest/language/function-already-defined.zeek
@@ -0,0 +1,11 @@
+# @TEST-EXEC-FAIL: zeek -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+function foo(a: string)
+	{ print a; }
+
+function foo(a: string)
+	{ }
+
+event zeek_init()
+	{ foo("hello"); }