diff --git a/README.markdown b/README.markdown
index bf7ff336b..a6aaaf952 100644
--- a/README.markdown
+++ b/README.markdown
@@ -274,7 +274,7 @@ The author of the Silk icon set is Mark James.
                             (like 0.65) or a percentage over layer height (like 200%)
         --first-layer-extrusion-width
                             Set a different extrusion width for first layer
-        --perimeters-extrusion-width
+        --perimeter-extrusion-width
                             Set a different extrusion width for perimeters
         --infill-extrusion-width
                             Set a different extrusion width for infill
@@ -285,7 +285,7 @@ The author of the Silk icon set is Mark James.
        Multiple extruder options:
         --extruder-offset   Offset of each extruder, if firmware doesn't handle the displacement
                             (can be specified multiple times, default: 0x0)
-        --perimeters-extruder
+        --perimeter-extruder
                             Extruder to use for perimeters (1+, default: 1)
         --infill-extruder   Extruder to use for infill (1+, default: 1)
         --support-material-extruder
diff --git a/slic3r.pl b/slic3r.pl
index d109f9ff4..2a1ef7eb4 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -322,7 +322,7 @@ $j
                         (like 0.65) or a percentage over layer height (like 200%)
     --first-layer-extrusion-width
                         Set a different extrusion width for first layer
-    --perimeters-extrusion-width
+    --perimeter-extrusion-width
                         Set a different extrusion width for perimeters
     --infill-extrusion-width
                         Set a different extrusion width for infill
@@ -333,7 +333,7 @@ $j
    Multiple extruder options:
     --extruder-offset   Offset of each extruder, if firmware doesn't handle the displacement
                         (can be specified multiple times, default: 0x0)
-    --perimeters-extruder
+    --perimeter-extruder
                         Extruder to use for perimeters (1+, default: 1)
     --infill-extruder   Extruder to use for infill (1+, default: 1)
     --support-material-extruder