diff --git a/src/main/kotlin/org/wycliffeassociates/otter/common/utils/RxUtils.kt b/src/main/kotlin/org/wycliffeassociates/otter/common/utils/RxUtils.kt
new file mode 100644
index 0000000..7d9a6c5
--- /dev/null
+++ b/src/main/kotlin/org/wycliffeassociates/otter/common/utils/RxUtils.kt
@@ -0,0 +1,14 @@
+package org.wycliffeassociates.otter.common.utils
+
+import io.reactivex.Observable
+
+/**
+ * Apply the given function as with `map()`, but remove any resulting nulls from the
+ * observable stream.
+ *
+ * This is how `observable.map(f).filter { it != null }` should behave, but it keeps
+ * nulls from ever appearing in an Observable, which would cause a crash in that
+ * two-step map/filter example.
+ */
+fun <T, R:Any> Observable<T>.mapNotNull(f: (T) -> R?): Observable<R> =
+    concatMapIterable { listOfNotNull(f(it)) }
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