diff --git a/lib/pure/httpclient.nim b/lib/pure/httpclient.nim
index fd0ef3856476f..f6c867adfbd3b 100644
--- a/lib/pure/httpclient.nim
+++ b/lib/pure/httpclient.nim
@@ -838,6 +838,7 @@ proc parseResponse(client: HttpClient | AsyncHttpClient,
   var parsedStatus = false
   var linei = 0
   var fullyRead = false
+  var prevHeader = ""
   var line = ""
   result.headers = newHttpHeaders()
   while true:
@@ -873,13 +874,24 @@ proc parseResponse(client: HttpClient | AsyncHttpClient,
     else:
       # Parse headers
       var name = ""
+      var leadingSpaces = skipWhitespace(line, linei)
       var le = parseUntil(line, name, ':', linei)
-      if le <= 0: httpError("invalid headers")
-      inc(linei, le)
-      if line[linei] != ':': httpError("invalid headers")
-      inc(linei) # Skip :
+      # We only check lines that have `:` in them and don't have
+      # leading whitespace, so non-header lines are just ignored
+      if le < line.len:
+        if leadingSpaces == 0 and le < line.len:
+          if le <= 0: httpError("invalid headers")
+          prevHeader = name
+          inc(linei, le)
+          if line[linei] != ':': httpError("invalid headers")
+          inc(linei) # Skip :
+          result.headers.add(name, line[linei .. ^1].strip())
+        # If there are spaces before the header name, it's actually a value
+        # that should be appended to the previous header, see bug #19261
+        # Also, if there was no header before this, we just ignore the line
+        elif prevHeader != "":
+          result.headers.table[result.headers.toCaseInsensitive(prevHeader)][^1].add line.strip()
 
-      result.headers.add(name, line[linei .. ^1].strip())
       if result.headers.len > headerLimit:
         httpError("too many headers")
 
diff --git a/lib/pure/httpcore.nim b/lib/pure/httpcore.nim
index 3b5cbc3cfc9e5..93ed1590b4c1b 100644
--- a/lib/pure/httpcore.nim
+++ b/lib/pure/httpcore.nim
@@ -126,7 +126,7 @@ func toTitleCase(s: string): string =
     result[i] = if upper: toUpperAscii(s[i]) else: toLowerAscii(s[i])
     upper = s[i] == '-'
 
-func toCaseInsensitive(headers: HttpHeaders, s: string): string {.inline.} =
+func toCaseInsensitive*(headers: HttpHeaders, s: string): string {.inline.} =
   return if headers.isTitleCase: toTitleCase(s) else: toLowerAscii(s)
 
 func newHttpHeaders*(titleCase=false): HttpHeaders =