diff --git a/python/ql/src/semmle/python/regex.qll b/python/ql/src/semmle/python/regex.qll
index 652c89147a29..913695b2acd2 100644
--- a/python/ql/src/semmle/python/regex.qll
+++ b/python/ql/src/semmle/python/regex.qll
@@ -68,7 +68,8 @@ abstract class RegexString extends Expr {
     /** Whether there is a character class, between start (inclusive) and end (exclusive) */
     predicate charSet(int start, int end) {
         exists(int inner_start, int inner_end |
-            this.char_set_start(start, inner_start) |
+            this.char_set_start(start, inner_start) and
+            not this.char_set_start(_, start) |
             end = inner_end + 1 and inner_end > inner_start and
             this.nonEscapedCharAt(inner_end) = "]" and
             not exists(int mid | this.nonEscapedCharAt(mid) = "]" |
diff --git a/python/ql/test/library-tests/regex/Characters.expected b/python/ql/test/library-tests/regex/Characters.expected
index f490522dc4c4..61d13b7bf59b 100644
--- a/python/ql/test/library-tests/regex/Characters.expected
+++ b/python/ql/test/library-tests/regex/Characters.expected
@@ -56,6 +56,11 @@
 | \\A[+-]?\\d+ | 3 | 4 |
 | \\A[+-]?\\d+ | 4 | 5 |
 | \\A[+-]?\\d+ | 7 | 9 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 0 | 2 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 12 | 13 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 16 | 18 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 18 | 20 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 30 | 31 |
 | \\\|\\[\\][123]\|\\{\\} | 0 | 2 |
 | \\\|\\[\\][123]\|\\{\\} | 2 | 4 |
 | \\\|\\[\\][123]\|\\{\\} | 4 | 6 |
diff --git a/python/ql/test/library-tests/regex/FirstLast.expected b/python/ql/test/library-tests/regex/FirstLast.expected
index 52ec6df203a7..cdea10fac051 100644
--- a/python/ql/test/library-tests/regex/FirstLast.expected
+++ b/python/ql/test/library-tests/regex/FirstLast.expected
@@ -45,6 +45,9 @@
 | \\A[+-]?\\d+ | first | 0 | 2 |
 | \\A[+-]?\\d+ | last | 7 | 9 |
 | \\A[+-]?\\d+ | last | 7 | 10 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | first | 0 | 2 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | last | 28 | 32 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | last | 28 | 33 |
 | \\\|\\[\\][123]\|\\{\\} | first | 0 | 2 |
 | \\\|\\[\\][123]\|\\{\\} | first | 12 | 14 |
 | \\\|\\[\\][123]\|\\{\\} | last | 6 | 11 |
diff --git a/python/ql/test/library-tests/regex/GroupContents.expected b/python/ql/test/library-tests/regex/GroupContents.expected
index 708579303024..c7c4ac97a1e3 100644
--- a/python/ql/test/library-tests/regex/GroupContents.expected
+++ b/python/ql/test/library-tests/regex/GroupContents.expected
@@ -10,7 +10,9 @@
 | (?P<name>[\\w]+)\| | 0 | 15 | (?P<name>[\\w]+) | 9 | 14 | [\\w]+ |
 | (?m)^(?!$) | 5 | 10 | (?!$) | 8 | 9 | $ |
 | (\\033\|~{) | 0 | 9 | (\\033\|~{) | 1 | 8 | \\033\|~{ |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 2 | 16 | (?P<txt>[^[]*) | 10 | 15 | [^[]* |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 20 | 34 | (?P<uri>[^)]*) | 28 | 33 | [^)]* |
 | ^(^y\|^z)(u$\|v$)$ | 1 | 8 | (^y\|^z) | 2 | 7 | ^y\|^z |
 | ^(^y\|^z)(u$\|v$)$ | 8 | 15 | (u$\|v$) | 9 | 14 | u$\|v$ |
 | ^[A-Z_]+$(?<!not-this) | 9 | 22 | (?<!not-this) | 13 | 21 | not-this |
-| x\|(?<!\\w)l | 2 | 9 | (?<!\\w) | 6 | 8 | \\w |
\ No newline at end of file
+| x\|(?<!\\w)l | 2 | 9 | (?<!\\w) | 6 | 8 | \\w |
diff --git a/python/ql/test/library-tests/regex/Qualified.expected b/python/ql/test/library-tests/regex/Qualified.expected
index 622938a2cd74..d3cf69b986f3 100644
--- a/python/ql/test/library-tests/regex/Qualified.expected
+++ b/python/ql/test/library-tests/regex/Qualified.expected
@@ -6,7 +6,9 @@
 | (?P<name>[\\w]+)\| | 9 | 14 | false |
 | \\A[+-]?\\d+ | 2 | 7 | true |
 | \\A[+-]?\\d+ | 7 | 10 | false |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 10 | 15 | true |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | 28 | 33 | true |
 | ^[A-Z_]+$(?<!not-this) | 1 | 8 | false |
 | ax{01,3} | 1 | 8 | false |
 | ax{3,} | 1 | 6 | false |
-| ax{,3} | 1 | 6 | true |
\ No newline at end of file
+| ax{,3} | 1 | 6 | true |
diff --git a/python/ql/test/library-tests/regex/Regex.expected b/python/ql/test/library-tests/regex/Regex.expected
index 008607eabc9e..92707f375944 100644
--- a/python/ql/test/library-tests/regex/Regex.expected
+++ b/python/ql/test/library-tests/regex/Regex.expected
@@ -121,6 +121,18 @@
 | \\A[+-]?\\d+ | qualified | 2 | 7 |
 | \\A[+-]?\\d+ | qualified | 7 | 10 |
 | \\A[+-]?\\d+ | sequence | 0 | 10 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char | 0 | 2 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char | 12 | 13 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char | 16 | 18 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char | 18 | 20 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char | 30 | 31 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char-set | 10 | 14 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | char-set | 28 | 32 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | non-empty group | 2 | 16 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | non-empty group | 20 | 34 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | qualified | 10 | 15 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | qualified | 28 | 33 |
+| \\[(?P<txt>[^[]*)\\]\\((?P<uri>[^)]*) | sequence | 0 | 34 |
 | \\\|\\[\\][123]\|\\{\\} | char | 0 | 2 |
 | \\\|\\[\\][123]\|\\{\\} | char | 2 | 4 |
 | \\\|\\[\\][123]\|\\{\\} | char | 4 | 6 |
diff --git a/python/ql/test/library-tests/regex/test.py b/python/ql/test/library-tests/regex/test.py
index 44b2825dcc34..6e57b9f7c716 100644
--- a/python/ql/test/library-tests/regex/test.py
+++ b/python/ql/test/library-tests/regex/test.py
@@ -57,3 +57,6 @@
 
 #Named group with caret and empty choice.
 re.compile(r'(?:(?P<n1>^(?:|x)))')
+
+#Misparsed on LGTM
+re.compile(r"\[(?P<txt>[^[]*)\]\((?P<uri>[^)]*)")
diff --git a/python/ql/test/query-tests/Expressions/Regex/test.py b/python/ql/test/query-tests/Expressions/Regex/test.py
index 535765573944..f0967dc6eefe 100644
--- a/python/ql/test/query-tests/Expressions/Regex/test.py
+++ b/python/ql/test/query-tests/Expressions/Regex/test.py
@@ -136,3 +136,6 @@
 
 #Named group with caret and empty choice.
 re.compile(r'(?:(?P<n1>^(?:|x)))')
+
+#Potentially mis-parsed character set
+re.compile(r"\[(?P<txt>[^[]*)\]\((?P<uri>[^)]*)")