diff --git a/src/core.ts b/src/core.ts
index 6bb582f..a7fce11 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -227,7 +227,7 @@ export interface MergeSignature {
     s5: Stream<T5>,
     s6: Stream<T6>,
     s7: Stream<T7>,
-    s8: Stream<T7>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8>;
+    s8: Stream<T8>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8>;
   <T1, T2, T3, T4, T5, T6, T7, T8, T9>(
     s1: Stream<T1>,
     s2: Stream<T2>,
@@ -236,8 +236,8 @@ export interface MergeSignature {
     s5: Stream<T5>,
     s6: Stream<T6>,
     s7: Stream<T7>,
-    s8: Stream<T7>,
-    s9: Stream<T7>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9>;
+    s8: Stream<T8>,
+    s9: Stream<T9>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9>;
   <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
     s1: Stream<T1>,
     s2: Stream<T2>,
@@ -246,9 +246,9 @@ export interface MergeSignature {
     s5: Stream<T5>,
     s6: Stream<T6>,
     s7: Stream<T7>,
-    s8: Stream<T7>,
-    s9: Stream<T7>,
-    s10: Stream<T7>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10>;
+    s8: Stream<T8>,
+    s9: Stream<T9>,
+    s10: Stream<T10>): Stream<T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10>;
   <T>(...stream: Array<Stream<T>>): Stream<T>;
 }