diff --git a/liberapay/testing/vcr.py b/liberapay/testing/vcr.py
index ac489d3ba..ed5525b4d 100644
--- a/liberapay/testing/vcr.py
+++ b/liberapay/testing/vcr.py
@@ -37,7 +37,7 @@ def serialize(cassette_dict):
 
     @staticmethod
     def deserialize(cassette_str):
-        return yaml.load(cassette_str, Loader=yaml.Loader)
+        return yaml.safe_load(cassette_str)
 
 
 vcr = VCR(
diff --git a/tests/py/fixtures/TestElsewhere.yml b/tests/py/fixtures/TestElsewhere.yml
index 70d25df08..35f8b3fd8 100644
--- a/tests/py/fixtures/TestElsewhere.yml
+++ b/tests/py/fixtures/TestElsewhere.yml
@@ -72,7 +72,7 @@ interactions:
     method: GET
     uri: https://bitbucket.org/api/2.0/users/adhsjakdjsdkjsajdhksda
   response:
-    body: {string: !!python/unicode '{"type": "error", "error": {"message": "adhsjakdjsdkjsajdhksda"}}'}
+    body: {string: '{"type": "error", "error": {"message": "adhsjakdjsdkjsajdhksda"}}'}
     headers:
       content-length: ['65']
       content-type: [application/json; charset=utf-8]
@@ -108,7 +108,7 @@ interactions:
     method: GET
     uri: https://gitlab.com/api/v4/users?username=adhsjakdjsdkjsajdhksda
   response:
-    body: {string: !!python/unicode '[]'}
+    body: {string: '[]'}
     headers:
       cache-control: ['max-age=0, private, must-revalidate']
       content-length: ['2']
@@ -126,12 +126,12 @@ interactions:
       vary: [Origin]
     status: {code: 200, message: OK}
 - request:
-    body: !!python/unicode client_secret=o090sc7828d7gljtrqc5n4vcpx3bfx&grant_type=client_credentials&client_id=9ro3g4slh0de5yijy6rqb2p0jgd7hi
+    body: client_secret=o090sc7828d7gljtrqc5n4vcpx3bfx&grant_type=client_credentials&client_id=9ro3g4slh0de5yijy6rqb2p0jgd7hi
     headers: {}
     method: POST
     uri: https://id.twitch.tv/oauth2/token
   response:
-    body: {string: !!python/unicode '{"access_token":"l5v4ham8prjwrvowu1pd1pue81t1qp","expires_in":5281481,"token_type":"bearer"}
+    body: {string: '{"access_token":"l5v4ham8prjwrvowu1pd1pue81t1qp","expires_in":5281481,"token_type":"bearer"}
 
 '}
     headers:
@@ -145,7 +145,7 @@ interactions:
     method: GET
     uri: https://api.twitch.tv/helix/users?login=adhsjakdjsdkjsajdhksda
   response:
-    body: {string: !!python/unicode '{"data":[]}'}
+    body: {string: '{"data":[]}'}
     headers:
       access-control-allow-origin: ['*']
       cache-control: ['no-cache, no-store, must-revalidate, private']
@@ -191,7 +191,7 @@ interactions:
     method: GET
     uri: https://bitbucket.org/api/2.0/users/%3E%27%3E%22%3E%3Cimg%20src%3Dx%20onerror%3Dalert%280%29%3E
   response:
-    body: {string: !!python/unicode ''}
+    body: {string: ''}
     headers:
       content-length: ['0']
       content-type: [text/html; charset=utf-8]
@@ -227,7 +227,7 @@ interactions:
     method: GET
     uri: https://gitlab.com/api/v4/users?username=%3E%27%3E%22%3E%3Cimg%20src%3Dx%20onerror%3Dalert%280%29%3E
   response:
-    body: {string: !!python/unicode '[]'}
+    body: {string: '[]'}
     headers:
       cache-control: ['max-age=0, private, must-revalidate']
       content-length: ['2']
@@ -250,7 +250,7 @@ interactions:
     method: GET
     uri: https://api.twitch.tv/helix/users?login=%3E%27%3E%22%3E%3Cimg%20src%3Dx%20onerror%3Dalert%280%29%3E
   response:
-    body: {string: !!python/unicode '{"error":"Bad Request","status":400,"message":"Error
+    body: {string: '{"error":"Bad Request","status":400,"message":"Error
         (400): Invalid login parameter requested: \u003e''\u003e\"\u003e\u003cimg
         src=x onerror=alert(0)\u003e"}'}
     headers:
diff --git a/tests/py/fixtures/TestPayinRefund.yml b/tests/py/fixtures/TestPayinRefund.yml
index 324f0efcd..aa549ec68 100644
--- a/tests/py/fixtures/TestPayinRefund.yml
+++ b/tests/py/fixtures/TestPayinRefund.yml
@@ -1,6 +1,6 @@
 interactions:
 - request:
-    body: !!python/unicode '{"CreditedWalletId": "43046470", "SecureModeReturnURL":
+    body: '{"CreditedWalletId": "43046470", "SecureModeReturnURL":
       "http://localhost/", "Fees": {"Currency": "EUR", "Amount": 65}, "DebitedFunds":
       {"Currency": "EUR", "Amount": 2065}, "SecureMode": "DEFAULT", "AuthorId": "43046469",
       "Tag": "584343568", "CardId": "43046475"}'
@@ -26,7 +26,7 @@ interactions:
       pragma: [no-cache]
     status: {code: 200, message: OK}
 - request:
-    body: !!python/unicode '{"DebitedFunds": {"Currency": "EUR", "Amount": 2000},
+    body: '{"DebitedFunds": {"Currency": "EUR", "Amount": 2000},
       "Tag": "584343569", "AuthorId": "43046469", "Payin": "43046758", "Fees": {"Currency":
       "EUR", "Amount": 0}}'
     headers: {}
diff --git a/tests/py/fixtures/TestRoutes.yml b/tests/py/fixtures/TestRoutes.yml
index 1df151b37..c3569fe80 100644
--- a/tests/py/fixtures/TestRoutes.yml
+++ b/tests/py/fixtures/TestRoutes.yml
@@ -5,7 +5,7 @@ interactions:
     method: GET
     uri: https://api.sandbox.mangopay.com/v2.01/liberapay-dev/cards/20717494
   response:
-    body: {string: !!python/unicode '{"ExpirationDate":"1234","Alias":"356999XXXXXX0132","CardType":"CB_VISA_MASTERCARD","CardProvider":"MASTERCARD","Country":"USA","Product":"   ","BankCode":"unknown","Active":true,"Currency":"EUR","Validity":"VALID","UserId":"20717491","Id":"20717494","Tag":null,"CreationDate":1486643837}'}
+    body: {string: '{"ExpirationDate":"1234","Alias":"356999XXXXXX0132","CardType":"CB_VISA_MASTERCARD","CardProvider":"MASTERCARD","Country":"USA","Product":"   ","BankCode":"unknown","Active":true,"Currency":"EUR","Validity":"VALID","UserId":"20717491","Id":"20717494","Tag":null,"CreationDate":1486643837}'}
     headers:
       cache-control: [no-cache]
       content-length: ['288']
@@ -22,7 +22,7 @@ interactions:
     method: PUT
     uri: https://api.sandbox.mangopay.com/v2.01/liberapay-dev/cards/20717494
   response:
-    body: {string: !!python/unicode '{"ExpirationDate":"1234","Alias":"356999XXXXXX0132","CardType":"CB_VISA_MASTERCARD","CardProvider":"MASTERCARD","Country":"USA","Product":"   ","BankCode":"unknown","Active":false,"Currency":"EUR","Validity":"VALID","UserId":"20717491","Id":"20717494","Tag":null,"CreationDate":1486643837}'}
+    body: {string: '{"ExpirationDate":"1234","Alias":"356999XXXXXX0132","CardType":"CB_VISA_MASTERCARD","CardProvider":"MASTERCARD","Country":"USA","Product":"   ","BankCode":"unknown","Active":false,"Currency":"EUR","Validity":"VALID","UserId":"20717491","Id":"20717494","Tag":null,"CreationDate":1486643837}'}
     headers:
       cache-control: [no-cache]
       content-length: ['289']