diff --git a/dist/index.js b/dist/index.js
index 25dfe89..cd3eb0c 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -62282,7 +62282,7 @@ function prepareDockerArgs(destinations) {
                         .map(s => s.trim())
                         .map(s => {
                           const equalIndex = s.indexOf('=');
-                          const key        = s.substring(0, equalIndex - 1);
+                          const key        = s.substring(0, equalIndex);
                           const value      = s.substring(equalIndex + 1);
                           return {
                             key,
diff --git a/src/lib.js b/src/lib.js
index 240ef07..59c9def 100644
--- a/src/lib.js
+++ b/src/lib.js
@@ -180,7 +180,7 @@ export function prepareDockerArgs(destinations) {
                         .map(s => s.trim())
                         .map(s => {
                           const equalIndex = s.indexOf('=');
-                          const key        = s.substring(0, equalIndex - 1);
+                          const key        = s.substring(0, equalIndex);
                           const value      = s.substring(equalIndex + 1);
                           return {
                             key,