diff --git a/src/boot/boot.janet b/src/boot/boot.janet
index 380f2863..922b759e 100644
--- a/src/boot/boot.janet
+++ b/src/boot/boot.janet
@@ -908,7 +908,7 @@
         (while true
           (if (= nil (set k1 (next i1 k1))) (break))
           (if (= nil (set k2 (next i2 k2))) (break))
-          (if (= nil (set k3 (next i2 k3))) (break))
+          (if (= nil (set k3 (next i3 k3))) (break))
           (array/push res (f (in i1 k1) (in i2 k2) (in i3 k3)))))
     4 (do
         (var k1 nil)
@@ -918,8 +918,8 @@
         (while true
           (if (= nil (set k1 (next i1 k1))) (break))
           (if (= nil (set k2 (next i2 k2))) (break))
-          (if (= nil (set k3 (next i2 k3))) (break))
-          (if (= nil (set k4 (next i2 k4))) (break))
+          (if (= nil (set k3 (next i3 k3))) (break))
+          (if (= nil (set k4 (next i4 k4))) (break))
           (array/push res (f (in i1 k1) (in i2 k2) (in i3 k3) (in i4 k4)))))
     (do
       (def iterkeys (array/new-filled ninds))
diff --git a/test/suite0001.janet b/test/suite0001.janet
index 7501f37a..958449ce 100644
--- a/test/suite0001.janet
+++ b/test/suite0001.janet
@@ -288,6 +288,11 @@
 (assert (deep= (map + [1 2 3] [10 20 30] [100 200 300] [1000 2000 3000]) @[1111 2222 3333]))
 (assert (deep= (map + [1 2 3] [10 20 30] [100 200 300] [1000 2000 3000] [10000 20000 30000]) @[11111 22222 33333]))
 
+# Mapping uses the shortest sequence
+(assert (deep= (map + [1 2 3 4] [10 20 30]) @[11 22 33]))
+(assert (deep= (map + [1 2 3 4] [10 20 30] [100 200]) @[111 222]))
+(assert (deep= (map + [1 2 3 4] [10 20 30] [100 200] [1000]) @[1111]))
+
 # Sort function
 (assert (deep=
           (range 99)