diff --git a/protocol/x/affiliates/keeper/grpc_query.go b/protocol/x/affiliates/keeper/grpc_query.go
index 63b10dca48..84185382a8 100644
--- a/protocol/x/affiliates/keeper/grpc_query.go
+++ b/protocol/x/affiliates/keeper/grpc_query.go
@@ -59,6 +59,13 @@ func (k Keeper) ReferredBy(ctx context.Context,
 	req *types.ReferredByRequest) (*types.ReferredByResponse, error) {
 	sdkCtx := sdk.UnwrapSDKContext(ctx)
 
+	// Check req.Address is a valid bech32 address
+	_, err := sdk.AccAddressFromBech32(req.GetAddress())
+	if err != nil {
+		return nil, errorsmod.Wrapf(types.ErrInvalidAddress, "address: %s, error: %s",
+			req.GetAddress(), err.Error())
+	}
+
 	affiliateAddr, exists := k.GetReferredBy(sdkCtx, req.GetAddress())
 	if !exists {
 		return &types.ReferredByResponse{}, nil
diff --git a/protocol/x/affiliates/keeper/grpc_query_test.go b/protocol/x/affiliates/keeper/grpc_query_test.go
index a19d76c3a9..23f0e35c93 100644
--- a/protocol/x/affiliates/keeper/grpc_query_test.go
+++ b/protocol/x/affiliates/keeper/grpc_query_test.go
@@ -190,6 +190,14 @@ func TestReferredBy(t *testing.T) {
 			expected:    nil,
 			expectError: nil,
 		},
+		"Invalid bech32 address": {
+			req: &types.ReferredByRequest{
+				Address: "Foo",
+			},
+			setup:       func(ctx sdk.Context, k keeper.Keeper) {},
+			expected:    nil,
+			expectError: types.ErrInvalidAddress,
+		},
 	}
 
 	for name, tc := range testCases {