diff --git a/interpreters/toywasm/regen.sh b/interpreters/toywasm/regen.sh
index 361a3bdcb..5d93bad5d 100755
--- a/interpreters/toywasm/regen.sh
+++ b/interpreters/toywasm/regen.sh
@@ -18,8 +18,16 @@ git -C ${DIR} checkout FETCH_HEAD
 # Note: for this build, TOYWASM_USE_SHORT_ENUMS is only used for
 # the "toywasm --version" output.
 
+# Note: Disable TOYWASM_USE_TAILCALL because it isn't safe for some
+# targets and/or compilers. For example, xtensa windowed ABI doesn't
+# allow tail call optimization. (At least it isn't straightforward
+# unless frame sizes of the caller and the callee happens to match.)
+# REVISIT: This should probably be a Kconfig knob. For now, disable
+# it globally.
+
 cmake -B ${BUILDDIR} \
 -DTOYWASM_USE_SHORT_ENUMS=OFF \
+-DTOYWASM_USE_TAILCALL=OFF \
 -DTOYWASM_ENABLE_WASM_EXTENDED_CONST=ON \
 -DTOYWASM_ENABLE_WASM_MULTI_MEMORY=ON \
 -DTOYWASM_ENABLE_WASM_TAILCALL=ON \