diff --git a/WoofWare.Expect.Test/SimpleTest.fs b/WoofWare.Expect.Test/SimpleTest.fs
index c7a20dd..d5c5acc 100644
--- a/WoofWare.Expect.Test/SimpleTest.fs
+++ b/WoofWare.Expect.Test/SimpleTest.fs
@@ -27,7 +27,7 @@ actual was:
 
             return
                 Assert
-                    .Throws<Exception>(fun () ->
+                    .Throws<ExpectException>(fun () ->
                         expectWithMockedFilePath ("filepath.fs", 99) {
                             snapshot "123"
                             return 124
diff --git a/WoofWare.Expect/Library.fs b/WoofWare.Expect/Library.fs
index 2bfc555..b5b39b4 100644
--- a/WoofWare.Expect/Library.fs
+++ b/WoofWare.Expect/Library.fs
@@ -15,6 +15,9 @@ type private SnapshotValue =
     | BareString of string
     | Json of string
 
+/// An exception indicating that a value failed to match its snapshot.
+exception ExpectException of Message : string
+
 /// A dummy type which is here to provide better error messages when you supply
 /// the `snapshot` keyword multiple times.
 type YouHaveSuppliedMultipleSnapshots = private | NonConstructible
@@ -160,25 +163,29 @@ type ExpectBuilder (?sourceOverride : string * int) =
                     JsonSerializer.Serialize (actual, options) |> JsonDocument.Parse
 
                 if not (JsonElement.DeepEquals (canonicalActual.RootElement, canonicalSnapshot.RootElement)) then
-                    failwithf
+                    sprintf
                         "snapshot mismatch! snapshot at %s:%i (%s) was:\n\n%s\n\nactual was:\n\n%s"
                         (sourceOverride |> Option.map fst |> Option.defaultValue source.FilePath)
                         (sourceOverride |> Option.map snd |> Option.defaultValue source.LineNumber)
                         source.MemberName
                         (canonicalSnapshot.RootElement.ToString () |> Text.predent '-')
                         (canonicalActual.RootElement.ToString () |> Text.predent '-')
+                    |> ExpectException
+                    |> raise
 
             | SnapshotValue.BareString snapshot ->
                 let actual = actual.ToString ()
 
                 if actual <> snapshot then
-                    failwithf
+                    sprintf
                         "snapshot mismatch! snapshot at %s:%i (%s) was:\n\n%s\n\nactual was:\n\n%s"
                         (sourceOverride |> Option.map fst |> Option.defaultValue source.FilePath)
                         (sourceOverride |> Option.map snd |> Option.defaultValue source.LineNumber)
                         source.MemberName
                         (snapshot |> Text.predent '-')
                         (actual |> Text.predent '+')
+                    |> ExpectException
+                    |> raise
 
         | None, _ -> failwith "Must specify snapshot"
         | _, None -> failwith "Must specify actual value with 'return'"
diff --git a/WoofWare.Expect/SurfaceBaseline.txt b/WoofWare.Expect/SurfaceBaseline.txt
index 5d8e006..d70148d 100644
--- a/WoofWare.Expect/SurfaceBaseline.txt
+++ b/WoofWare.Expect/SurfaceBaseline.txt
@@ -11,6 +11,12 @@ WoofWare.Expect.ExpectBuilder.Return [method]: unit -> 'T WoofWare.Expect.Expect
 WoofWare.Expect.ExpectBuilder.Run [method]: (unit -> 'T WoofWare.Expect.ExpectState) -> unit
 WoofWare.Expect.ExpectBuilder.Snapshot [method]: (unit WoofWare.Expect.ExpectState, string, string option, int option, string option) -> WoofWare.Expect.YouHaveSuppliedMultipleSnapshots WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectBuilder.SnapshotJson [method]: (unit WoofWare.Expect.ExpectState, string, string option, int option, string option) -> WoofWare.Expect.YouHaveSuppliedMultipleSnapshots WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectException inherit System.Exception, implements System.Collections.IStructuralEquatable
+WoofWare.Expect.ExpectException..ctor [constructor]: string
+WoofWare.Expect.ExpectException..ctor [constructor]: unit
+WoofWare.Expect.ExpectException.Equals [method]: (System.Exception, System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.ExpectException.Equals [method]: System.Exception -> bool
+WoofWare.Expect.ExpectException.Message [property]: [read-only] string
 WoofWare.Expect.ExpectState`1 inherit obj, implements 'T WoofWare.Expect.ExpectState System.IEquatable, System.Collections.IStructuralEquatable, 'T WoofWare.Expect.ExpectState System.IComparable, System.IComparable, System.Collections.IStructuralComparable
 WoofWare.Expect.ExpectState`1.Equals [method]: ('T WoofWare.Expect.ExpectState, System.Collections.IEqualityComparer) -> bool
 WoofWare.Expect.YouHaveSuppliedMultipleSnapshots inherit obj, implements WoofWare.Expect.YouHaveSuppliedMultipleSnapshots System.IEquatable, System.Collections.IStructuralEquatable, WoofWare.Expect.YouHaveSuppliedMultipleSnapshots System.IComparable, System.IComparable, System.Collections.IStructuralComparable