diff --git a/packages/rstream/src/index.ts b/packages/rstream/src/index.ts
index 4f10c477ad..55b1d5e66e 100644
--- a/packages/rstream/src/index.ts
+++ b/packages/rstream/src/index.ts
@@ -19,6 +19,7 @@ export * from "./from/raf";
 export * from "./from/view";
 export * from "./from/worker";
 
+export * from "./subs/asidechain";
 export * from "./subs/bisect";
 export * from "./subs/post-worker";
 export * from "./subs/resolve";
diff --git a/packages/rstream/src/subs/asidechain.ts b/packages/rstream/src/subs/asidechain.ts
new file mode 100644
index 0000000000..4a819f5bd0
--- /dev/null
+++ b/packages/rstream/src/subs/asidechain.ts
@@ -0,0 +1,27 @@
+import { CommonOpts } from "../api";
+import { Subscription } from "../subscription";
+
+/**
+ * Abstract base class for sidechained subscription types (e.g.
+ * {@link sidechainPartition}, {@link sidechainToggle}).
+ */
+export abstract class ASidechain<A, S, B> extends Subscription<A, B> {
+    sideSub!: Subscription<any, S>;
+
+    constructor(opts?: Partial<CommonOpts>) {
+        super(undefined, opts);
+    }
+
+    unsubscribe(sub?: Subscription<any, any>) {
+        const res = super.unsubscribe(sub);
+        if (!sub || !this.subs.length) {
+            this.sideSub.unsubscribe();
+        }
+        return res;
+    }
+
+    done() {
+        this.sideSub.unsubscribe();
+        super.done();
+    }
+}
diff --git a/packages/rstream/src/subs/sidechain-partition.ts b/packages/rstream/src/subs/sidechain-partition.ts
index ca57758879..a33c992a34 100644
--- a/packages/rstream/src/subs/sidechain-partition.ts
+++ b/packages/rstream/src/subs/sidechain-partition.ts
@@ -2,6 +2,7 @@ import { Predicate } from "@thi.ng/api";
 import { CommonOpts, ISubscribable, State } from "../api";
 import { Subscription } from "../subscription";
 import { optsWithID } from "../utils/idgen";
+import { ASidechain } from "./asidechain";
 
 export interface SidechainPartitionOpts<T> extends CommonOpts {
     pred: Predicate<T>;
@@ -39,16 +40,15 @@ export const sidechainPartition = <A, B>(
     opts?: Partial<SidechainPartitionOpts<B>>
 ): Subscription<A, A[]> => new SidechainPartition<A, B>(side, opts);
 
-export class SidechainPartition<A, B> extends Subscription<A, A[]> {
-    sideSub: Subscription<B, B>;
-    buf: A[];
+export class SidechainPartition<T, S> extends ASidechain<T, S, T[]> {
+    buf: T[];
 
     constructor(
-        side: ISubscribable<B>,
-        opts?: Partial<SidechainPartitionOpts<B>>
+        side: ISubscribable<S>,
+        opts?: Partial<SidechainPartitionOpts<S>>
     ) {
         opts = optsWithID("sidepart", opts);
-        super(undefined, opts);
+        super(opts);
         this.buf = [];
         const pred = opts.pred || (() => true);
         const $this = this;
@@ -69,22 +69,9 @@ export class SidechainPartition<A, B> extends Subscription<A, A[]> {
         });
     }
 
-    unsubscribe(sub?: Subscription<any, any>) {
-        const res = super.unsubscribe(sub);
-        if (!sub || !this.subs.length) {
-            this.sideSub.unsubscribe();
-        }
-        return res;
-    }
-
-    next(x: A) {
+    next(x: T) {
         if (this.state < State.DONE) {
             this.buf.push(x);
         }
     }
-
-    done() {
-        this.sideSub.unsubscribe();
-        super.done();
-    }
 }
diff --git a/packages/rstream/src/subs/sidechain-toggle.ts b/packages/rstream/src/subs/sidechain-toggle.ts
index d68d1a0c26..fd79879571 100644
--- a/packages/rstream/src/subs/sidechain-toggle.ts
+++ b/packages/rstream/src/subs/sidechain-toggle.ts
@@ -1,7 +1,8 @@
 import { Predicate } from "@thi.ng/api";
-import { CommonOpts, ISubscribable } from "../api";
+import { CommonOpts, ISubscribable, State } from "../api";
 import { Subscription } from "../subscription";
 import { optsWithID } from "../utils/idgen";
+import { ASidechain } from "./asidechain";
 
 export interface SidechainToggleOpts<T> extends CommonOpts {
     pred: Predicate<T>;
@@ -41,16 +42,15 @@ export const sidechainToggle = <A, B>(
     opts?: Partial<SidechainToggleOpts<B>>
 ): Subscription<A, A> => new SidechainToggle(side, opts);
 
-export class SidechainToggle<A, B> extends Subscription<A, A> {
-    sideSub: Subscription<B, B>;
+export class SidechainToggle<T, S> extends ASidechain<T, S, T> {
     isActive: boolean;
 
     constructor(
-        side: ISubscribable<B>,
-        opts?: Partial<SidechainToggleOpts<B>>
+        side: ISubscribable<S>,
+        opts?: Partial<SidechainToggleOpts<S>>
     ) {
         opts = optsWithID("sidetoggle", opts);
-        super(undefined, opts);
+        super(opts);
         this.isActive = !!opts.initial;
         const pred = opts.pred || (() => true);
         const $this = this;
@@ -66,22 +66,9 @@ export class SidechainToggle<A, B> extends Subscription<A, A> {
         });
     }
 
-    unsubscribe(sub?: Subscription<any, any>) {
-        const res = super.unsubscribe(sub);
-        if (!sub || !this.subs.length) {
-            this.sideSub.unsubscribe();
-        }
-        return res;
-    }
-
-    next(x: A) {
-        if (this.isActive) {
+    next(x: T) {
+        if (this.isActive && this.state < State.DONE) {
             super.next(x);
         }
     }
-
-    done() {
-        super.done();
-        this.sideSub.unsubscribe();
-    }
 }