diff --git a/tests/generate.zsh b/tests/generate.zsh
index 64a1ede..ef89f94 100755
--- a/tests/generate.zsh
+++ b/tests/generate.zsh
@@ -31,6 +31,9 @@
 emulate -LR zsh
 setopt localoptions extendedglob
 
+# Required for add-zle-hook-widget.
+zmodload zsh/zle
+
 # Argument parsing.
 if (( $# != 3 )) || [[ $1 == -* ]]; then
   print -r -- >&2 "$0: usage: $0 BUFFER HIGHLIGHTER BASENAME"
diff --git a/tests/test-highlighting.zsh b/tests/test-highlighting.zsh
index 812b1a7..e5c85a1 100755
--- a/tests/test-highlighting.zsh
+++ b/tests/test-highlighting.zsh
@@ -31,6 +31,9 @@
 
 setopt NO_UNSET WARN_CREATE_GLOBAL
 
+# Required for add-zle-hook-widget.
+zmodload zsh/zle
+
 # Check an highlighter was given as argument.
 [[ -n "$1" ]] || {
   echo >&2 "Bail out! You must provide the name of a valid highlighter as argument."
diff --git a/tests/test-perfs.zsh b/tests/test-perfs.zsh
index 3411754..49d95c7 100755
--- a/tests/test-perfs.zsh
+++ b/tests/test-perfs.zsh
@@ -29,6 +29,9 @@
 # -------------------------------------------------------------------------------------------------
 
 
+# Required for add-zle-hook-widget.
+zmodload zsh/zle
+
 # Check an highlighter was given as argument.
 [[ -n "$1" ]] || {
   echo >&2 "Bail out! You must provide the name of a valid highlighter as argument."