diff --git a/packages/mermaid/src/themes/theme-default.js b/packages/mermaid/src/themes/theme-default.js
index c149b43f34..d95ccf59e0 100644
--- a/packages/mermaid/src/themes/theme-default.js
+++ b/packages/mermaid/src/themes/theme-default.js
@@ -187,6 +187,7 @@ class Theme {
     this.loopTextColor = this.actorTextColor;
     this.noteBorderColor = this.border2;
     this.noteTextColor = this.actorTextColor;
+    this.actorLineColor = this.actorBorder;
 
     /* Gantt chart variables */
 
diff --git a/packages/mermaid/src/themes/theme-forest.js b/packages/mermaid/src/themes/theme-forest.js
index 077e07f9ea..4bb7d24413 100644
--- a/packages/mermaid/src/themes/theme-forest.js
+++ b/packages/mermaid/src/themes/theme-forest.js
@@ -101,6 +101,7 @@ class Theme {
     this.loopTextColor = this.actorTextColor;
     this.noteBorderColor = this.border2;
     this.noteTextColor = this.actorTextColor;
+    this.actorLineColor = this.actorBorder;
 
     /* Each color-set will have a background, a foreground and a border color */
     this.cScale0 = this.cScale0 || this.primaryColor;