diff --git a/src/widgets.zsh b/src/widgets.zsh
index 7fb1183..450ed3c 100644
--- a/src/widgets.zsh
+++ b/src/widgets.zsh
@@ -85,7 +85,7 @@ _zsh_autosuggest_modify() {
 
 	# Get a new suggestion if the buffer is not empty after modification
 	if (( $#BUFFER > 0 )); then
-		if (( ! ${+ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE} )) || (( $#BUFFER <= $ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE )); then
+		if [[ -z "$ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE" ]] || (( $#BUFFER <= $ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE )); then
 			_zsh_autosuggest_fetch
 		fi
 	fi
diff --git a/zsh-autosuggestions.zsh b/zsh-autosuggestions.zsh
index f6f6a84..16c6ccc 100644
--- a/zsh-autosuggestions.zsh
+++ b/zsh-autosuggestions.zsh
@@ -346,7 +346,7 @@ _zsh_autosuggest_modify() {
 
 	# Get a new suggestion if the buffer is not empty after modification
 	if (( $#BUFFER > 0 )); then
-		if (( ! ${+ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE} )) || (( $#BUFFER <= $ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE )); then
+		if [[ -z "$ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE" ]] || (( $#BUFFER <= $ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE )); then
 			_zsh_autosuggest_fetch
 		fi
 	fi