diff --git a/src/blocks.c b/src/blocks.c
index 68d514fc6..377cc0e64 100644
--- a/src/blocks.c
+++ b/src/blocks.c
@@ -755,22 +755,24 @@ static void S_find_first_nonspace(cmark_parser *parser, cmark_chunk *input) {
   char c;
   int chars_to_tab = TAB_STOP - (parser->column % TAB_STOP);
 
-  parser->first_nonspace = parser->offset;
-  parser->first_nonspace_column = parser->column;
-  while ((c = peek_at(input, parser->first_nonspace))) {
-    if (c == ' ') {
-      parser->first_nonspace += 1;
-      parser->first_nonspace_column += 1;
-      chars_to_tab = chars_to_tab - 1;
-      if (chars_to_tab == 0) {
+  if (parser->first_nonspace <= parser->offset) {
+    parser->first_nonspace = parser->offset;
+    parser->first_nonspace_column = parser->column;
+    while ((c = peek_at(input, parser->first_nonspace))) {
+      if (c == ' ') {
+        parser->first_nonspace += 1;
+        parser->first_nonspace_column += 1;
+        chars_to_tab = chars_to_tab - 1;
+        if (chars_to_tab == 0) {
+          chars_to_tab = TAB_STOP;
+        }
+      } else if (c == '\t') {
+        parser->first_nonspace += 1;
+        parser->first_nonspace_column += chars_to_tab;
         chars_to_tab = TAB_STOP;
+      } else {
+        break;
       }
-    } else if (c == '\t') {
-      parser->first_nonspace += 1;
-      parser->first_nonspace_column += chars_to_tab;
-      chars_to_tab = TAB_STOP;
-    } else {
-      break;
     }
   }
 
@@ -1373,6 +1375,9 @@ static void S_process_line(cmark_parser *parser, const unsigned char *buffer,
 
   parser->offset = 0;
   parser->column = 0;
+  parser->first_nonspace = 0;
+  parser->first_nonspace_column = 0;
+  parser->indent = 0;
   parser->blank = false;
   parser->partially_consumed_tab = false;
 
diff --git a/test/pathological_tests.py b/test/pathological_tests.py
index 9552b3996..ffe3bf9d6 100644
--- a/test/pathological_tests.py
+++ b/test/pathological_tests.py
@@ -69,21 +69,24 @@ def badhash(ref):
     "nested block quotes":
                  ((("> " * 50000) + "a"),
                   re.compile("(<blockquote>\n){50000}")),
+    "deeply nested lists":
+                 ("".join(map(lambda x: ("  " * x + "* a\n"), range(0,1000))),
+                  re.compile("<ul>\n(<li>a\n<ul>\n){999}<li>a</li>\n</ul>\n(</li>\n</ul>\n){999}")),
     "U+0000 in input":
                  ("abc\u0000de\u0000",
                   re.compile("abc\ufffd?de\ufffd?")),
     "backticks":
-                 ("".join(map(lambda x: ("e" + "`" * x), range(1,10000))),
+                 ("".join(map(lambda x: ("e" + "`" * x), range(1,5000))),
                   re.compile("^<p>[e`]*</p>\n$")),
     "unclosed links A":
-                 ("[a](<b" * 50000,
-                  re.compile("(\[a\]\(&lt;b){50000}")),
+                 ("[a](<b" * 30000,
+                  re.compile("(\[a\]\(&lt;b){30000}")),
     "unclosed links B":
-                 ("[a](b" * 50000,
-                  re.compile("(\[a\]\(b){50000}")),
-    "many references":
-                 ("".join(map(lambda x: ("[" + str(x) + "]: u\n"), range(1,50000 * 16))) + "[0] " * 50000,
-                  re.compile("(\[0\] ){49999}")),
+                 ("[a](b" * 30000,
+                  re.compile("(\[a\]\(b){30000}")),
+#    "many references":
+#                 ("".join(map(lambda x: ("[" + str(x) + "]: u\n"), range(1,5000 * 16))) + "[0] " * 5000,
+#                  re.compile("(\[0\] ){4999}")),
     "reference collisions": hash_collisions()
     }