diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index 78d0865b89..1992e7372e 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -359,25 +359,22 @@ func typeEncoder(t reflect.Type) encoderFunc {
 	}
 
 	// To deal with recursive types, populate the map with an
-	// indirect func before we build it. This type waits on the
-	// real func (f) to be ready and then calls it. This indirect
-	// func is only used for recursive types.
-	var (
-		wg sync.WaitGroup
-		f  encoderFunc
-	)
-	wg.Add(1)
+	// indirect func before we build it. If the type is recursive,
+	// the second lookup for the type will return the indirect func.
+	//
+	// This indirect func is only used for recursive types,
+	// and briefly during racing calls to typeEncoder.
+	indirect := sync.OnceValue(func() encoderFunc {
+		return newTypeEncoder(t, true)
+	})
 	fi, loaded := encoderCache.LoadOrStore(t, encoderFunc(func(e *encodeState, v reflect.Value, opts encOpts) {
-		wg.Wait()
-		f(e, v, opts)
+		indirect()(e, v, opts)
 	}))
 	if loaded {
 		return fi.(encoderFunc)
 	}
 
-	// Compute the real encoder and replace the indirect func with it.
-	f = newTypeEncoder(t, true)
-	wg.Done()
+	f := indirect()
 	encoderCache.Store(t, f)
 	return f
 }
diff --git a/src/encoding/json/encode_test.go b/src/encoding/json/encode_test.go
index bc31f9d48a..87074eabd4 100644
--- a/src/encoding/json/encode_test.go
+++ b/src/encoding/json/encode_test.go
@@ -16,7 +16,9 @@ import (
 	"regexp"
 	"runtime/debug"
 	"strconv"
+	"sync"
 	"testing"
+	"testing/synctest"
 	"time"
 )
 
@@ -1403,3 +1405,21 @@ func TestIssue63379(t *testing.T) {
 		}
 	}
 }
+
+// Issue #73733: encoding/json used a WaitGroup to coordinate access to cache entries.
+// Since WaitGroup.Wait is durably blocking, this caused apparent deadlocks when
+// multiple bubbles called json.Marshal at the same time.
+func TestSynctestMarshal(t *testing.T) {
+	var wg sync.WaitGroup
+	for range 5 {
+		wg.Go(func() {
+			synctest.Test(t, func(t *testing.T) {
+				_, err := Marshal([]string{})
+				if err != nil {
+					t.Errorf("Marshal: %v", err)
+				}
+			})
+		})
+	}
+	wg.Wait()
+}
diff --git a/src/encoding/json/v2_encode_test.go b/src/encoding/json/v2_encode_test.go
index 16e8d01218..11c5218649 100644
--- a/src/encoding/json/v2_encode_test.go
+++ b/src/encoding/json/v2_encode_test.go
@@ -16,7 +16,9 @@ import (
 	"regexp"
 	"runtime/debug"
 	"strconv"
+	"sync"
 	"testing"
+	"testing/synctest"
 	"time"
 )
 
@@ -1408,3 +1410,21 @@ func TestIssue63379(t *testing.T) {
 		}
 	}
 }
+
+// Issue #73733: encoding/json used a WaitGroup to coordinate access to cache entries.
+// Since WaitGroup.Wait is durably blocking, this caused apparent deadlocks when
+// multiple bubbles called json.Marshal at the same time.
+func TestSynctestMarshal(t *testing.T) {
+	var wg sync.WaitGroup
+	for range 5 {
+		wg.Go(func() {
+			synctest.Test(t, func(t *testing.T) {
+				_, err := Marshal([]string{})
+				if err != nil {
+					t.Errorf("Marshal: %v", err)
+				}
+			})
+		})
+	}
+	wg.Wait()
+}