diff --git a/CHANGES b/CHANGES
index d4fcef86e8..5db2968746 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,10 @@
+
+3.3.0-dev.113 | 2020-08-18 12:10:26 -0700
+
+  * GH-467: Catch use of &add_func/&delete_func on IDs without values. (Robin Sommer, Corelight)
+
+  * Fix compiler warning from missing namepsace qualification (Tim Wojtulewicz, Corelight)
+
 3.3.0-dev.109 | 2020-08-14 10:00:07 -0700
 
   * GH-178: Add new string bif methods based on python string utilities (Tim Wojtulewicz, Corelight)
diff --git a/VERSION b/VERSION
index b23bd4dfb6..74d1b59943 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.3.0-dev.109
+3.3.0-dev.113
diff --git a/src/ID.cc b/src/ID.cc
index 03f15e1f78..f607ab23c2 100644
--- a/src/ID.cc
+++ b/src/ID.cc
@@ -220,6 +220,13 @@ void ID::SetVal(ExprPtr ev, InitClass c)
 	if ( ! a )
 		Internal("no add/delete function in ID::SetVal");
 
+	if ( ! val )
+		{
+		Error(fmt("%s initializer applied to ID without value",
+		          c == INIT_EXTRA ? "+=" : "-="), this);
+		return;
+		}
+
 	EvalFunc(a->GetExpr(), std::move(ev));
 	}
 
diff --git a/testing/btest/Baseline/language.global-unset-addto/output b/testing/btest/Baseline/language.global-unset-addto/output
new file mode 100644
index 0000000000..306f0afddb
--- /dev/null
+++ b/testing/btest/Baseline/language.global-unset-addto/output
@@ -0,0 +1,2 @@
+error in /Users/robin/bro/master/testing/btest/.tmp/language.global-unset-addto/global-unset-addto.zeek, line 4: += initializer applied to ID without value (a)
+error in /Users/robin/bro/master/testing/btest/.tmp/language.global-unset-addto/global-unset-addto.zeek, line 5: -= initializer applied to ID without value (b)
diff --git a/testing/btest/language/global-unset-addto.zeek b/testing/btest/language/global-unset-addto.zeek
new file mode 100644
index 0000000000..bf2f794809
--- /dev/null
+++ b/testing/btest/language/global-unset-addto.zeek
@@ -0,0 +1,15 @@
+# @TEST-EXEC-FAIL: zeek -b %INPUT  >output 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff output
+
+global a: count &add_func = function(old: count, new: count): count { return 3; };
+global b: count &delete_func = function(old: count, new: count): count { return 3; };
+
+redef a += 13;
+redef b -= 13;
+
+# The following is ok.
+global c: count &redef &add_func = function(old: count, new: count): count { return 3; };
+redef c = 0;
+redef c += 13;
+
+