diff --git a/res/localization/rufus.loc b/res/localization/rufus.loc
index 0d14eececb3..625566fc972 100644
--- a/res/localization/rufus.loc
+++ b/res/localization/rufus.loc
@@ -487,6 +487,9 @@ t MSG_237 "Bad Blocks: Testing with pattern 0x%02X"
 # eg. "Partitioning (MBR)..."
 t MSG_238 "Partitioning (%s)..."
 t MSG_239 "Deleting partitions..."
+t MSG_240 "The signature for the downloaded update can not be validated. This could mean that your "
+	"system is improperly configured for signature validation or indicate a malicious download.\n\n"
+	"The download will be deleted. Please check the log for more details."
 t MSG_241 "Downloading: %0.1f%%"
 t MSG_242 "Failed to download file."
 t MSG_243 "Checking for Rufus updates..."
diff --git a/src/pki.c b/src/pki.c
index 25de1259393..00d01418916 100644
--- a/src/pki.c
+++ b/src/pki.c
@@ -53,7 +53,7 @@ const char* WinPKIErrorString(void)
 	static char error_string[64];
 	DWORD error_code = GetLastError();
 
-	if ((error_code >> 16) != 0x8009)
+	if (((error_code >> 16) != 0x8009) && ((error_code >> 16) != 0x800B))
 		return WindowsErrorString();
 
 	switch (error_code) {
@@ -113,6 +113,12 @@ const char* WinPKIErrorString(void)
 		return "Cannot complete usage check.";
 	case CRYPT_E_NO_TRUSTED_SIGNER:
 		return "None of the signers of the cryptographic message or certificate trust list is trusted.";
+	case CERT_E_UNTRUSTEDROOT:
+		return "The root certificate is not trusted.";
+	case TRUST_E_NOSIGNATURE:
+		return "Not digitally signed.";
+	case TRUST_E_EXPLICIT_DISTRUST:
+		return "One of the certificates used was marked as untrusted by the user.";
 	default:
 		static_sprintf(error_string, "Unknown PKI error 0x%08lX", error_code);
 		return error_string;
@@ -268,7 +274,13 @@ LONG ValidateSignature(HWND hDlg, const char* path)
 	}
 
 	trust_data.cbStruct = sizeof(trust_data);
-	trust_data.dwUIChoice = WTD_UI_ALL;
+	// NB: WTD_UI_ALL can result in ERROR_SUCCESS even if the signature validation fails,
+	// because it still prompts the user to run untrusted software, even after explicitly
+	// notifying them that the signature invalid (and of course Microsoft had to make
+	// that UI prompt a bit too similar to the other benign prompt you get when running
+	// trusted software, which, as per cert.org's assessment, may confuse non-security
+	// conscious-users who decide to gloss over these kind of notifications).
+	trust_data.dwUIChoice = WTD_UI_NONE;
 	// We just downloaded from the Internet, so we should be able to check revocation
 	trust_data.fdwRevocationChecks = WTD_REVOKE_WHOLECHAIN;
 	// 0x400 = WTD_MOTW  for Windows 8.1 or later
@@ -278,6 +290,19 @@ LONG ValidateSignature(HWND hDlg, const char* path)
 
 	r = WinVerifyTrust(NULL, &guid_generic_verify, &trust_data);
 	safe_free(trust_file.pcwszFilePath);
+	switch (r) {
+	case ERROR_SUCCESS:
+		break;
+	case TRUST_E_NOSIGNATURE:
+		// Should already have been reported, but since we have a custom message for it...
+		uprintf("PKI: File does not appear to be signed: %s", WinPKIErrorString());
+		MessageBoxExU(hDlg, lmprintf(MSG_284), lmprintf(MSG_283), MB_OK | MB_ICONERROR | MB_IS_RTL, selected_langid);
+		break;
+	default:
+		uprintf("PKI: Failed to validate signature: %s", WinPKIErrorString());
+		MessageBoxExU(hDlg, lmprintf(MSG_240), lmprintf(MSG_283), MB_OK | MB_ICONERROR | MB_IS_RTL, selected_langid);
+		break;
+	}
 
 	return r;
 }
diff --git a/src/rufus.rc b/src/rufus.rc
index 3f553eea754..0d0c2a73777 100644
--- a/src/rufus.rc
+++ b/src/rufus.rc
@@ -33,7 +33,7 @@ LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
 IDD_DIALOG DIALOGEX 12, 12, 242, 376
 STYLE DS_SETFONT | DS_MODALFRAME | DS_CENTER | WS_MINIMIZEBOX | WS_POPUP | WS_CAPTION | WS_SYSMENU
 EXSTYLE WS_EX_ACCEPTFILES
-CAPTION "Rufus 2.17.1186"
+CAPTION "Rufus 2.17.1187"
 FONT 8, "Segoe UI Symbol", 400, 0, 0x0
 BEGIN
     LTEXT           "Device",IDS_DEVICE_TXT,9,6,200,8
@@ -366,8 +366,8 @@ END
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 2,17,1186,0
- PRODUCTVERSION 2,17,1186,0
+ FILEVERSION 2,17,1187,0
+ PRODUCTVERSION 2,17,1187,0
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
  FILEFLAGS 0x1L
@@ -384,13 +384,13 @@ BEGIN
         BEGIN
             VALUE "CompanyName", "Akeo Consulting (http://akeo.ie)"
             VALUE "FileDescription", "Rufus"
-            VALUE "FileVersion", "2.17.1186"
+            VALUE "FileVersion", "2.17.1187"
             VALUE "InternalName", "Rufus"
             VALUE "LegalCopyright", "© 2011-2017 Pete Batard (GPL v3)"
             VALUE "LegalTrademarks", "http://www.gnu.org/copyleft/gpl.html"
             VALUE "OriginalFilename", "rufus.exe"
             VALUE "ProductName", "Rufus"
-            VALUE "ProductVersion", "2.17.1186"
+            VALUE "ProductVersion", "2.17.1187"
         END
     END
     BLOCK "VarFileInfo"
diff --git a/src/stdlg.c b/src/stdlg.c
index 29eccaef78c..bdec209f3ad 100644
--- a/src/stdlg.c
+++ b/src/stdlg.c
@@ -1674,8 +1674,12 @@ INT_PTR CALLBACK NewVersionCallback(HWND hDlg, UINT message, WPARAM wParam, LPAR
 			case 2:		// Launch newer version and close this one
 				Sleep(1000);	// Add a delay on account of antivirus scanners
 
-				if (ValidateSignature(hDlg, filepath) != NO_ERROR)
+				if (ValidateSignature(hDlg, filepath) != NO_ERROR) {
+					// Unconditionally delete the download and disable the "Launch" control
+					_unlinkU(filepath);
+					EnableWindow(GetDlgItem(hDlg, IDC_DOWNLOAD), FALSE);
 					break;
+				}
 
 				memset(&si, 0, sizeof(si));
 				memset(&pi, 0, sizeof(pi));