diff --git a/src/Array.ts b/src/Array.ts
index d49925c41..8f004ca91 100644
--- a/src/Array.ts
+++ b/src/Array.ts
@@ -404,7 +404,10 @@ export const chainWithIndex =
   (as: Array<A>): Array<B> => {
     const out: Array<B> = []
     for (let i = 0; i < as.length; i++) {
-      out.push(...f(i, as[i]))
+      const bs = f(i, as[i])
+      for (let j = 0; j < bs.length; j++) {
+        out.push(bs[j])
+      }
     }
     return out
   }
diff --git a/src/NonEmptyArray.ts b/src/NonEmptyArray.ts
index 4a135abcd..38a1df417 100644
--- a/src/NonEmptyArray.ts
+++ b/src/NonEmptyArray.ts
@@ -569,7 +569,10 @@ export const chainWithIndex =
   (as: NonEmptyArray<A>): NonEmptyArray<B> => {
     const out: NonEmptyArray<B> = fromReadonlyNonEmptyArray(f(0, head(as)))
     for (let i = 1; i < as.length; i++) {
-      out.push(...f(i, as[i]))
+      const bs = f(i, as[i])
+      for (let j = 0; j < bs.length; j++) {
+        out.push(bs[j])
+      }
     }
     return out
   }
diff --git a/src/ReadonlyArray.ts b/src/ReadonlyArray.ts
index fc413bd48..41c367086 100644
--- a/src/ReadonlyArray.ts
+++ b/src/ReadonlyArray.ts
@@ -289,7 +289,10 @@ export const chainWithIndex =
     }
     const out: Array<B> = []
     for (let i = 0; i < as.length; i++) {
-      out.push(...f(i, as[i]))
+      const bs = f(i, as[i])
+      for (let j = 0; j < bs.length; j++) {
+        out.push(bs[j])
+      }
     }
     return out
   }
diff --git a/src/ReadonlyNonEmptyArray.ts b/src/ReadonlyNonEmptyArray.ts
index cce5f2713..65875678e 100644
--- a/src/ReadonlyNonEmptyArray.ts
+++ b/src/ReadonlyNonEmptyArray.ts
@@ -565,7 +565,10 @@ export const chainWithIndex =
   (as: ReadonlyNonEmptyArray<A>): ReadonlyNonEmptyArray<B> => {
     const out: NonEmptyArray<B> = _.fromReadonlyNonEmptyArray(f(0, head(as)))
     for (let i = 1; i < as.length; i++) {
-      out.push(...f(i, as[i]))
+      const bs = f(i, as[i])
+      for (let j = 0; j < bs.length; j++) {
+        out.push(bs[j])
+      }
     }
     return out
   }