diff --git a/src/crypto/x509/root_cgo_darwin.go b/src/crypto/x509/root_cgo_darwin.go
index 8e80533590..31c0c666ec 100644
--- a/src/crypto/x509/root_cgo_darwin.go
+++ b/src/crypto/x509/root_cgo_darwin.go
@@ -201,11 +201,20 @@ int FetchPEMRoots(CFDataRef *pemRoots, CFDataRef *untrustedPemRoots) {
 import "C"
 import (
 	"errors"
+	"io/ioutil"
+	"os"
 	"unsafe"
 )
 
 func loadSystemRoots() (*CertPool, error) {
 	roots := NewCertPool()
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
 
 	var data C.CFDataRef = nil
 	var untrustedData C.CFDataRef = nil
diff --git a/src/crypto/x509/root_darwin.go b/src/crypto/x509/root_darwin.go
index bc35a1cf21..21e52bec51 100644
--- a/src/crypto/x509/root_darwin.go
+++ b/src/crypto/x509/root_darwin.go
@@ -81,18 +81,26 @@ func execSecurityRoots() (*CertPool, error) {
 		)
 	}
 
-	cmd := exec.Command("/usr/bin/security", args...)
-	data, err := cmd.Output()
-	if err != nil {
-		return nil, err
-	}
-
 	var (
 		mu          sync.Mutex
 		roots       = NewCertPool()
 		numVerified int // number of execs of 'security verify-cert', for debug stats
 	)
 
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
+
+	cmd := exec.Command("/usr/bin/security", args...)
+	data, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+
 	blockCh := make(chan *pem.Block)
 	var wg sync.WaitGroup
 
diff --git a/src/crypto/x509/root_unix.go b/src/crypto/x509/root_unix.go
index 65b5a5fdbc..c9c7ac6a74 100644
--- a/src/crypto/x509/root_unix.go
+++ b/src/crypto/x509/root_unix.go
@@ -37,6 +37,13 @@ func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate
 
 func loadSystemRoots() (*CertPool, error) {
 	roots := NewCertPool()
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
 
 	files := certFiles
 	if f := os.Getenv(certFileEnv); f != "" {