diff --git a/scripts/fuzz_opt.py b/scripts/fuzz_opt.py
index e0950b58c9c..9a834e7647d 100755
--- a/scripts/fuzz_opt.py
+++ b/scripts/fuzz_opt.py
@@ -2370,6 +2370,7 @@ def write_commands(commands, filename):
                          ("--remove-unused-types",),
                          ("--abstract-type-refining",),
                          ("--cfp",),
+                         ("--cfp-reftest",),
                          ("--gsi",),
                          ("--type-ssa",),
                          ("--type-merging",)}
diff --git a/src/passes/ConstantFieldPropagation.cpp b/src/passes/ConstantFieldPropagation.cpp
index 26b3241d6fd..e2b75e88de8 100644
--- a/src/passes/ConstantFieldPropagation.cpp
+++ b/src/passes/ConstantFieldPropagation.cpp
@@ -549,6 +549,10 @@ struct ConstantFieldPropagation : public Pass {
       return;
     }
 
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "CFP requires --closed-world";
+    }
+
     // Find and analyze all writes inside each function.
     PCVFunctionStructValuesMap functionNewInfos(*module),
       functionSetInfos(*module);
diff --git a/test/lit/passes/cfp-desc.wast b/test/lit/passes/cfp-desc.wast
index aeda747547a..6a2587d3709 100644
--- a/test/lit/passes/cfp-desc.wast
+++ b/test/lit/passes/cfp-desc.wast
@@ -1,6 +1,6 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
-;; RUN: foreach %s %t wasm-opt --cfp -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --cfp --closed-world -all -S -o - | filecheck %s
 
 (module
   (rec
diff --git a/test/lit/passes/cfp-reftest-desc.wast b/test/lit/passes/cfp-reftest-desc.wast
index 7064276f2b4..d53cc428759 100644
--- a/test/lit/passes/cfp-reftest-desc.wast
+++ b/test/lit/passes/cfp-reftest-desc.wast
@@ -1,6 +1,6 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
-;; RUN: foreach %s %t wasm-opt --cfp-reftest -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --cfp-reftest --closed-world -all -S -o - | filecheck %s
 
 ;; When a ref.get_desc can only read from two types, and those types have a
 ;; constant field, we can select between those two values using a ref.test.
diff --git a/test/lit/passes/cfp-reftest.wast b/test/lit/passes/cfp-reftest.wast
index 404f3147234..48cda2bc226 100644
--- a/test/lit/passes/cfp-reftest.wast
+++ b/test/lit/passes/cfp-reftest.wast
@@ -1,6 +1,6 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
-;; RUN: foreach %s %t wasm-opt --cfp-reftest -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --cfp-reftest --closed-world -all -S -o - | filecheck %s
 
 ;; When a struct.get can only read from two types, and those types have a
 ;; constant field, we can select between those two values using a ref.test.
diff --git a/test/lit/passes/cfp-rmw.wast b/test/lit/passes/cfp-rmw.wast
index 02266796a48..57af1e6bc73 100644
--- a/test/lit/passes/cfp-rmw.wast
+++ b/test/lit/passes/cfp-rmw.wast
@@ -1,6 +1,6 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
-;; RUN: foreach %s %t wasm-opt --cfp -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --cfp --closed-world -all -S -o - | filecheck %s
 
 ;; RMW ops are generally writes that inhibit optimization.
 (module
diff --git a/test/lit/passes/cfp.wast b/test/lit/passes/cfp.wast
index de34fb7f4c2..81946889b05 100644
--- a/test/lit/passes/cfp.wast
+++ b/test/lit/passes/cfp.wast
@@ -1,6 +1,6 @@
 ;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
 
-;; RUN: foreach %s %t wasm-opt --remove-unused-names --cfp -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --remove-unused-names --cfp --closed-world -all -S -o - | filecheck %s
 
 ;; (remove-unused-names is added to test fallthrough values without a block
 ;; name getting in the way)